AI Audio Providers — Research & Reference (TTS + Music Generation)¶
Purpose. WorkWingman is adding provider-agnostic audio features: text-to-speech narration / "audio overviews" of study material, and optional AI-generated music for study soundtracks and podcast intro/outro stings. This is a research/reference doc (not a two-track technical/plain doc). It exists so a later docs/technical/ design + a .NET adapter can be written with the licensing and pricing landmines already mapped.
Model. Tiered BYOK (bring-your-own-key), mirroring ApiKeyProviderRegistry (src/WorkWingman.Infrastructure/Integrations/ApiKeyProviderRegistry.cs). Every provider row is Id, DisplayName, WhatItUnlocks, SignupUrl, Kind, IsFree, FreeTierNote, ConfigKey, IsWired. Hard rules that already govern the registry apply here verbatim:
- A free/local default always works with no key. Key absent → that premium provider shows unavailable, free carries on.
- The app never buys keys, never signs up on the user's behalf. It deep-links the user to
SignupUrl; the user pastes the key; it lands in the KeePass vault. - Sandbox never falls back to appsettings/env keys (see
ApiKeyProvider.cs) — same guarantee must hold for audio adapters.
As-of date: 2026-07-07. Pricing and licensing in this space move fast (see the caveat at the very bottom). Every non-obvious claim is cited inline.
TL;DR — recommended tiers¶
| Tier | TTS pick | Music pick | Why |
|---|---|---|---|
| Tier 0 — free/local default (keyless) | Kokoro-82M (Apache-2.0, bundled ONNX) | Meta MusicGen only if run as a personal, non-shared default; otherwise no keyless music — see landmine | Kokoro sounds like a real person, commercial-safe, ships in-app. MusicGen weights are CC-BY-NC → cannot license shared output. |
| Tier 1 — affordable BYO-key | OpenAI gpt-4o-mini-tts (~$0.015/min) or Amazon Polly Neural ($16/1M) |
Stability Stable Audio 2.5 or Beatoven.ai (perpetual royalty-free license) | Cheap, real REST APIs, clear commercial terms on paid tier. |
| Tier 2 — premium BYO-key | ElevenLabs (best-in-class, cloning/emotion) | ElevenLabs Music v2 (licensed-only training) or Google Lyria 3 (Vertex) | Highest quality; ElevenLabs Music v2 trained on cleared catalog = safest premium music. |
Best keyless default TTS: Kokoro (Apache-2.0). Realistically it sounds natural and human on normal-length narration; Piper is the fallback for very low-end CPUs but sounds more mechanical on long passages. Best keyless/local music: MusicGen technically runs locally, but its CC-BY-NC weights make its output unusable in anything the user shares/publishes — treat local music as "personal preview only," and gate any shareable music behind a Tier-1 BYO-key provider.
Licensing landmines (read before proposing anything)¶
- 🚑 Coqui XTTS v2 weights = non-commercial (CPML), and Coqui is defunct — no one to sell you a commercial license. Do not use for any user-shared audio. Code (MPL-2.0) is fine; the weights are the trap. (promptquorum)
- 🚑 Meta MusicGen / AudioCraft weights = CC-BY-NC-4.0. Code is MIT; you cannot sell or publish music made from the released weights. Fine as a personal-only preview; never as the engine behind content a user distributes. (HF discussion)
- ⚠️ Suno / Udio free tiers are non-commercial and the provider retains ownership. Even paid Suno now grants only a perpetual license to exploit, not copyright, and its ToS disclaims that any copyright vests at all. Neither exposes a first-party developer API — third-party "Suno API"/"Udio API" resellers are unofficial. (Suno commercial, Udio ToS)
- ⚠️ Free consumer tools ≠ licensed output. Google MusicFX (Labs) and Suno/Udio free tiers do not hand a clean commercial license; only the paid Lyria via Vertex does. (Lyria/MusicFX)
- ⚠️ Piper active fork is GPL-3.0 (was MIT). Usable commercially but copyleft — must disclose modifications if you ship a modified binary. Prefer Kokoro (Apache-2.0) as the bundled default to avoid the copyleft question entirely. (Piper license)
- ⚠️ OpenAI TTS requires an AI-disclosure to end users — you must tell listeners the voice is AI-generated. Trivial for us (an "AI narration" label), but it's a ToS obligation, not optional. (OpenAI TTS guide)
- ℹ️ Voice cloning everywhere requires documented consent (ElevenLabs, Resemble, WellSaid; and US state laws — CA §3344, NY §50-51, TN ELVIS Act). We are not cloning voices for narration, so this is out of scope — but if a "clone my own voice" feature is ever added, consent capture is mandatory. (ElevenLabs consent)
A) Premium Text-to-Speech APIs (narration / audio overviews)¶
All prices are BYO-key, pay-as-you-go, per 1M characters unless noted. "Commercial output OK?" = can the end user publish/share audio they generate.
| Provider | Public REST API + auth | Quality / notable | Price (BYO-key) | Free tier | Commercial output OK? | Gotchas |
|---|---|---|---|---|---|---|
| ElevenLabs | Yes, xi-api-key header (docs) |
Best-in-class realism; instant voice cloning, emotion (v3), streaming, ~300–500ms round-trip, 30+ langs | $0.10/1M (Multilingual v2/v3); $0.05/1M (Flash/Turbo) (API pricing) | Yes but non-commercial; commercial needs paid Starter $5/mo+ (BIGVU) | Yes on paid plan | Cloning needs consent; ElevenLabs keeps a license to your uploaded voice data to train models (policy) |
| OpenAI TTS | Yes, Authorization: Bearer, POST /v1/audio/speech (docs) |
13 voices on gpt-4o-mini-tts (steerable by instructions); streaming; mp3/opus/aac/flac/wav/pcm |
gpt-4o-mini-tts ~$0.015/min; tts-1 $15/1M, tts-1-hd $30/1M (pricing) |
No standing free tier (usage-billed) | Yes | Must disclose voice is AI to end users (ToS) (guide) |
| Google Cloud TTS | Yes, POST /v1/text:synthesize, OAuth/service-account or API key (docs) |
Chirp 3 HD (newest), Neural2, Studio; SSML; mp3/LINEAR16/OGG_OPUS; 40+ langs | Neural2 $16/1M, Chirp3-HD $30/1M, Studio $160/1M (pricing) | 1M chars/mo free (Chirp3/Neural2/Studio); 4M for WaveNet/Standard | Yes | Auth is service-account JSON, heavier than an API key; BYO-key UX = "paste GCP key" |
| Azure Neural TTS | Yes, Speech SDK/REST, subscription key (pricing) | Large voice/lang catalog; Neural HD; SSML; custom neural voice (enterprise) | Neural $16/1M, Neural HD $22/1M, commitment tiers down to $7.50/1M (TextToLab) | 500K chars/mo free | Yes (prebuilt); Personal Voice is consent-gated / not for commercial | Custom Neural Voice adds endpoint-hosting + training fees |
| Amazon Polly (Neural) | Yes, AWS SDK/SigV4 (pricing) | Neural + Generative + Long-Form engines; SSML; mp3/ogg/pcm; solid, not top-tier realism | Neural $16/1M; Generative $30/1M; Long-Form $100/1M; Standard $4/1M | 1M Neural chars/mo for 12 mo; free tier has no commercial restriction | Yes | SigV4 auth (BYO = access key + secret, two fields) |
| Cartesia (Sonic) | Yes, API key (docs) | #1 naturalness claims, ~40–90ms latency, 40+ langs, streaming, laughter/emotion | ~$35/1M (Sonic 3) (eesel) | Free $0 (20K credits/mo, non-commercial); commercial = Pro $5/mo (pricing) | Yes on Pro+ | Real-time-agent-oriented; overkill for batch narration but great if we want live playback |
| Deepgram (Aura-2) | Yes, API key (pricing) | Sub-90ms latency, agent-focused; per-1K-char billing | $30/1M PAYG, $27/1M growth | $200 free credit | Yes | Fewer voices/langs than the big cloud vendors |
| PlayHT | Yes, API key | Large voice library, cloning | Creator $39/mo (50K words), Pro $99/mo (g2) | 5K words/mo (non-commercial) | Paid tiers only | Commercial rights restricted to paid (freetts matrix) |
| Rime | Yes, API key (pricing) | Conversational/"spoken-style" voices, low latency | $75/1M | 10K chars/mo free | Yes on paid | Niche voice style; not general narration first choice |
| WellSaid Labs | Yes (Studio + API) | Enterprise narration, studio-trained pro-talent voices | Creative $50/mo/user (awesomeagents) | Trial only | Yes but enterprise contract; some voices restrict political content | Built for enterprise; heavy for a BYO consumer |
| Resemble AI | Yes, API key | Deep emotional/voice-param control, cloning | Free 12.5K chars/mo; paid from ~$374/yr for 3M (typecast) | 12.5K chars/mo | Paid tiers | Cloning consent required |
| Hume (Octave) | Yes, API key (docs) | Emotionally expressive, prompted with natural-language emotion cues (no SSML) | $30/1M PAYG (pricing) | Free/Starter = non-commercial; commercial = Creator $14/mo | Creator+ only | Great for "warm study narrator" tone; commercial gate at $14/mo |
| Murf | Yes, API key (API plans) | Studio-quality + Falcon conversational | Studio $30/1M, Falcon $10/1M; $10/mo free API credit | $10/mo API credit | Yes (paid, Creator+) | Two API models at different quality/price |
Free / local tier (keyless, bundled)¶
| Engine | License | Quality reality | Commercial output? | Fit |
|---|---|---|---|---|
| Kokoro-82M | Apache-2.0 (HF) | "Sounds like a real person" — natural intonation, smooth prosody; 54 quality-graded voices, 8 langs; 82M params, runs on CPU (RTF ~0.03 on GPU); 24kHz WAV native (review) | Yes — fully commercial | ✅ Recommended Tier-0 default |
| Piper | GPL-3.0 (active fork; was MIT) | Clear but more mechanical on long passages; 900+ voices, 35+ langs; ~30–50ms first-audio, king of Raspberry-Pi/edge (codesota) | Yes (copyleft — disclose mods) | ✅ Fallback for very low-end CPUs |
| Coqui / XTTS v2 | Code MPL-2.0; weights CPML = NON-COMMERCIAL | Best open multilingual voice-cloning quality | 🚑 NO — non-commercial weights, vendor defunct | ❌ Do not use for shared audio |
| Windows SAPI | OS built-in | Robotic legacy voices | Yes (OS) | ⚠️ Last-resort only if no bundled model; poor quality |
B) AI Music Generation APIs (study soundtrack / podcast stings)¶
Emphasis: is there a real API (not just a web app)? and commercial/ownership terms.
| Provider | Real API? | Quality / notable | Price | Commercial / ownership | Verdict |
|---|---|---|---|---|---|
| ElevenLabs Music v2 | Yes — POST /v1/music (docs) |
Studio-grade; trained on licensed-only catalog; section inpainting, embedded SFX; mp3/pcm/opus | $0.15/min (API) (pricing) | Cleared for commercial on paid plan; licensed-only training = strongest legal footing | ✅ Best premium Tier-2 music |
| Stability Stable Audio 2.5 | Yes — Developer Platform API, credits (platform) | Trained on licensed AudioSparx catalog; instrumental focus | Credit-based (1 credit=$0.01), 25 free credits (stableaudio) | Commercial on paid; free access for orgs under $1M/yr revenue (license) | ✅ Good affordable Tier-1 |
| Google Lyria 3 (Vertex) | Yes — Vertex AI API (public preview) (docs) | Lyria 3 (30s clips) / Lyria 3 Pro (up to 184s, vocals) | Lyria 2 ~$0.06/30s (blog) | Paid Vertex = commercial; free MusicFX Labs does not grant a clean license | ✅ Premium alt (needs GCP) |
| Beatoven.ai | Yes — API | Mood/scene-based custom tracks for video | Subscription | Perpetual royalty-free license, survives cancellation (beatoven) | ✅ Creator-friendly Tier-1 |
| Mubert | Yes — API for apps/games/streams (api) | 200+ moods; loop/stream-oriented royalty-free | Subscription | Sync license for video/podcast/app/game (license) | ✅ Good for ambient study loops |
| Meta MusicGen / AudioCraft | Local (MIT code) + hosted on Replicate (replicate) | Text→music; medium model needs ~16GB GPU | Free (local) / Replicate per-run | 🚑 Weights CC-BY-NC — output NOT licensable for sharing (HF) | ⚠️ Local personal-preview only, never shared output |
| Stable Audio Open 1.0 | Local weights (HF) | Open self-host variant | Free (self-host) | Community license — check per-use; more permissive than MusicGen but read terms (HF) | ⚠️ Possible future local option; verify license before shipping |
| AIVA | Limited/enterprise | Composition tool | Free / Std / Pro | Copyright only transfers on Pro; Free/Std = AIVA keeps copyright (wavespeed) | ⚠️ Ownership gated to Pro |
| Loudly / Soundraw | Loudly has API; Soundraw web-first | Stem/loop hybrid, section reshaping; trained on own catalogs (sidesteps label disputes) | Subscription | Royalty-free on paid plans | ⚠️ OK Tier-1 alt; confirm API access |
| Suno | No first-party API (only unofficial resellers) | Top consumer quality | Consumer subscription | Free = non-commercial + Suno owns; paid = perpetual license, not copyright; ToS disclaims copyright vesting (dynamoi) | ❌ No official API — do not propose |
| Udio | No first-party consumer API; v4 "Enterprise API" exists but gated (musicmake) | Top consumer quality, 48kHz | Consumer subscription | Free = Udio owns; Pro/Enterprise = you own | ❌ Not a BYO-key consumer API — skip |
| Google MusicFX | No API (Labs web tool) | Free consumer demo | Free | No clean commercial license | ❌ Web-only, unlicensed — do not propose |
| Riffusion | Developer/customization niche API | Spectrogram-based | Varies | Commercial on paid | ℹ️ Niche; not a first pick |
Consumer-web-only (no usable BYO API) → do NOT propose: Suno (first-party), Udio (consumer), Google MusicFX.
C) Recommendation — tiered registry mapping¶
Concrete ApiKeyProviderRegistry rows to add (Kind = CredentialKind.ApiKey unless noted). IsWired = false until the adapter exists.
Tier 0 — free/local default (keyless, no registry row needed)¶
| Feature | Engine | Why |
|---|---|---|
| TTS narration / audio overview | Kokoro-82M bundled ONNX | Apache-2.0, natural voice, CPU-capable, 24kHz WAV — always-on default with zero key. |
| Music (personal preview only) | MusicGen local (optional, gated "not for shared content") | Runs locally but CC-BY-NC → never feed into user-published audio. If we don't want the licensing footgun, ship no keyless music and require a Tier-1 key for any shareable soundtrack. |
Tier 1 — affordable BYO-key¶
| Id | DisplayName | WhatItUnlocks | SignupUrl | IsFree | ConfigKey | Why |
|---|---|---|---|---|---|---|
tts-openai |
OpenAI TTS | Higher-quality narration (gpt-4o-mini-tts) |
https://platform.openai.com/api-keys | false | WorkWingman:OpenAiTtsApiKey |
~$0.015/min, one API key, clear commercial rights (must show AI-voice label). |
tts-polly |
Amazon Polly (Neural) | Cheap high-volume narration | https://aws.amazon.com/polly/ | false | WorkWingman:PollyAccessKey (+:PollySecretKey) |
$16/1M, 12-mo free tier with no commercial restriction. |
music-stableaudio |
Stability Stable Audio | Royalty-free study/intro music | https://platform.stability.ai/ | true | WorkWingman:StableAudioApiKey |
Licensed-catalog training; free for <$1M-rev users; cheap credits. |
music-beatoven |
Beatoven.ai | Mood-based royalty-free soundtracks | https://www.beatoven.ai/ | true | WorkWingman:BeatovenApiKey |
Perpetual license survives cancellation — safest creator terms. |
Tier 2 — premium BYO-key¶
| Id | DisplayName | WhatItUnlocks | SignupUrl | IsFree | ConfigKey | Why |
|---|---|---|---|---|---|---|
tts-elevenlabs |
ElevenLabs | Best-in-class narration, emotion | https://elevenlabs.io/app/settings/api-keys | true | WorkWingman:ElevenLabsApiKey |
Top realism; free tier exists but commercial needs Starter $5/mo. |
tts-google |
Google Cloud TTS | Chirp 3 HD narration, 40+ langs | https://console.cloud.google.com/apis/credentials | true | WorkWingman:GoogleTtsApiKey |
1M free chars/mo; reuses existing Google-Cloud BYO pattern. |
music-elevenlabs |
ElevenLabs Music | Cleared, licensed-only AI music | https://elevenlabs.io/app/settings/api-keys | true | WorkWingman:ElevenLabsApiKey (shared) |
$0.15/min; licensed-only training = strongest premium-music legal footing. |
music-lyria |
Google Lyria (Vertex) | Structured tracks w/ vocals | https://console.cloud.google.com/ | false | WorkWingman:GoogleTtsApiKey (shared GCP) |
Paid Vertex grants commercial license; Pro up to 184s. |
IsFree flag note: set IsFree = true where a genuinely free tier exists for the key itself (ElevenLabs, Google, Stable Audio, Beatoven all have free tiers, even if commercial use needs the cheapest paid plan — mirror the FMR/Udemy convention where IsFree means "free to obtain," with the caveat in FreeTierNote). Set IsFree = false for OpenAI/Polly/Lyria which are usage-billed with no standing free tier.
Bad-fit flags for user-shared content: Coqui/XTTS (non-commercial weights), MusicGen (CC-BY-NC weights), Suno/Udio free tiers (provider-owned, no official API), MusicFX (no license, no API). None of these should back any audio a user publishes.
D) Integration notes (for the later .NET adapter)¶
TTS #1 — Kokoro (Tier-0 local default)¶
- No HTTP. Load
kokoro-v1.0.onnx+voices-v1.0.binviaMicrosoft.ML.OnnxRuntime; output is a float sample buffer at 24000 Hz, write to WAV (NAudio/libsndfile). (kokoro-onnx, ONNX weights) - Pick voice by id (e.g.
af_sarah),speedfloat,lang="en-us". Batch (no streaming needed for overviews). Convert WAV→MP3 with a bundled encoder if smaller files wanted.
TTS #2 — OpenAI (Tier-1 batch)¶
POST https://api.openai.com/v1/audio/speech, headerAuthorization: Bearer <key>.- Body:
{ "model": "gpt-4o-mini-tts", "input": "<text>", "voice": "alloy", "response_format": "mp3", "speed": 1.0 }. response_format∈mp3|opus|aac|flac|wav|pcm. Response body = raw audio bytes (stream to file). Supports chunked streaming for play-while-generating. (docs)
TTS #3 — Google Cloud TTS (Tier-2 batch)¶
POST https://texttospeech.googleapis.com/v1/text:synthesize, auth via API key or service-account bearer.- Body:
{ "input": {"text": "..."}, "voice": {"languageCode":"en-US","name":"en-US-Chirp3-HD-..."}, "audioConfig": {"audioEncoding":"MP3"} }. audioEncoding∈LINEAR16|MP3|OGG_OPUS. Response JSON has base64audioContent(decode → file). Batch only (no low-latency stream for narration). (docs)
Music #1 — ElevenLabs Music (Tier-2)¶
POST https://api.elevenlabs.io/v1/music, headerxi-api-key: <key>.- Simple:
{ "prompt": "calm lo-fi study beat", "music_length_ms": 30000 }(music_length_ms3000–600000; can't combinepromptwithcomposition_plan). - Output format string
codec_sample_rate_bitrate, defaultmp3_48000_192; also PCM/opus/u-law/a-law. Streaming endpoint available (/v1/music/stream). (compose docs)
Music #2 — Stability Stable Audio (Tier-1)¶
- Stability Developer Platform REST endpoint, API-key auth, credit-based (1 credit=$0.01). Text-prompt → audio; instrumental focus. Confirm current endpoint path + max duration at build time. (platform)
Adapter shape. One IAudioNarrator seam (Kokoro default + OpenAI/Google/ElevenLabs BYO adapters) and one IMusicGenerator seam (Stable Audio/Beatoven/ElevenLabs/Lyria BYO adapters), each resolving its key through IApiKeyProvider.Get(id) exactly like the existing GeminiImageSource/OpenAiImageSource do. Absent key → adapter reports unavailable; Kokoro carries narration; music simply hidden. Sandbox never reads appsettings keys.
Subscriptions vs. API keys — what users may already have¶
The BYO-key screen asks the user to paste an API key. A common (and expensive) misconception is that a consumer subscription — ChatGPT Plus, Gemini Advanced, an ElevenLabs Creator plan — comes with a usable API key. For most providers it does not: the consumer chat/app subscription and the developer API are separate accounts with separate billing. This section web-verifies the 2026 reality so our UI copy never misleads a subscriber into thinking they're already set up. As-of 2026-07-07.
1. OpenAI — Plus/Pro subscription ≠ API key (confirmed, unchanged)¶
- A ChatGPT Plus ($20/mo) or Pro ($200/mo) subscription does NOT include API access, an API key, or API credits. It only upgrades the chat web/app interface. (OpenAI Help — billing in ChatGPT vs Platform)
platform.openai.comis a fully separate, pay-as-you-go account with its own billing. Even Pro/Business/Enterprise chat subscriptions give no API credit and no API discount. (ToolColumn — subscription vs API billing)- No standing free API tier. API usage is billed per token from the first call; you must add a payment method / prepay credits on the platform account. So a user with only a ChatGPT subscription has no usable key and must set up separate API billing to use our OpenAI TTS adapter.
2. Google — the free AI Studio key is the real win; the consumer sub is not it¶
Two very different things share the "Gemini" brand — keep them apart:
- (a) FREE Google AI Studio Gemini API key — go to aistudio.google.com, create a key, and get a genuinely free API tier: Gemini Flash / Flash-Lite at ~1,500 requests/day, 1M tokens/min, no credit card required. (Gemini API free tier, TokenMix — 1,500 req/day, no card) Caveat: in April 2026 Google moved Pro models to paid-only; the free tier is now Flash-only, and free-tier prompts may be used to improve Google's products. This is the key we already use for
gemini-image— the same AI-Studio key. - (b) Vertex AI (Chirp 3 HD TTS, Lyria 3 music) — these are NOT on the free AI Studio key. They require a Google Cloud project with billing enabled (service-account or GCP API key), billed per character / per 30s. (Lyria on Vertex)
- Consumer subscription grants NEITHER. Google AI Pro / Gemini Advanced / Google One AI Premium (~$19.99/mo) does NOT include API access — it's a consumer chat subscription (Gemini app, 100 prompts/day, Deep Research, etc.). It gives no Gemini API key and no Vertex access. (AIonX — Gemini Advanced API access, pecollective — free tier guide)
Bottom line for Google: point users at the free AI Studio key for anything that model supports; only the (separately-billed, GCP-project) Vertex path unlocks Chirp3 TTS / Lyria music — and never imply their $19.99 Gemini sub covers either.
3. ElevenLabs / Amazon / Stability / Beatoven¶
- ElevenLabs — subscription DOES include API (the one exception). From Starter ($5–6/mo) upward, API access is included on the same account, drawing from the same shared monthly credit pool as the web app — there's no separate API account. (ElevenLabs pricing, Flexprice breakdown) So an existing ElevenLabs paid subscriber already has a usable API key in their account settings. (Free plan can generate an API key too, but its output is non-commercial.)
- Amazon Polly — needs a separate AWS account (not Prime). There's no "Polly subscription." The user signs up for AWS (separate from their amazon.com/Prime account), creates an IAM access-key + secret, and is billed pay-as-you-go; a card is required even for the 12-month free tier. (AWS — signing up, Polly IAM) BYO here is two fields (access key + secret), not one.
- Stability AI — Developer Platform API is separate from the consumer "Stable Assistant" subscription. The API is pay-as-you-go credits ($10/1,000 credits after 25 free). A Stable Assistant chat/image subscription does not hand you a Platform API key. (Stability Developer Platform) (25 free credits let a user try our music adapter with no spend.)
- Beatoven — API is a separate, contact-gated key. Consumer plans (Creator ~$2.50/mo etc.) are for the web app; API access requires emailing
hello@beatoven.aito be issued an API key for your app. A normal subscriber does not automatically have an API key. (Beatoven API)
Honest messaging table (what the UI may safely tell the user)¶
For each provider: does something the user might already own give them a usable API key? And the exact one-liner we can show without lying.
| Provider | If you already have… | Usable key? | Safe one-liner for the UI |
|---|---|---|---|
| OpenAI TTS | ChatGPT Plus / Pro | NO | "Your ChatGPT subscription does not include an API key. Create a separate, pay-as-you-go key at platform.openai.com." |
| Google (Gemini API models) | nothing | YES — free | "Get a free Google AI Studio API key — no credit card, generous free tier." ⭐ |
| Google Chirp 3 / Lyria (Vertex) | Google AI Pro / One AI Premium | NO | "Your Gemini subscription doesn't cover this. Chirp 3 TTS / Lyria music need a Google Cloud project with billing enabled." |
| ElevenLabs | An ElevenLabs paid plan (Starter+) | YES | "Already subscribed to ElevenLabs? Your paid plan includes API access — copy your key from ElevenLabs → Settings → API Keys." |
| Amazon Polly | Amazon Prime | NO | "Prime doesn't count — Polly needs a separate AWS account. Create an IAM access key (pay-as-you-go; free tier available)." |
| Stability Stable Audio | Stable Assistant subscription | NO (but 25 free credits) | "The consumer app plan isn't the API. Grab a Developer Platform key — 25 free credits to start." |
| Beatoven | A Beatoven web-app plan | NO | "Beatoven's API key is issued on request — email hello@beatoven.ai to enable it for the app." |
Emphasis for the UI:
- ⭐ Genuinely free to grab (no card): the Google AI Studio Gemini API key — this is the one to surface first and label "Free." It's the only recommended provider where a brand-new user gets a working key at zero cost and no billing setup.
- 💳 Pay-as-you-go, separate billing (set expectations): OpenAI, Amazon Polly, Google Vertex (Chirp3/Lyria), Stability (after 25 free credits) — all require the user to create a developer account and add a payment method; their existing consumer subscription won't help.
- ✅ Subscription already includes the key: only ElevenLabs — an existing paid subscriber can reuse their key directly; everyone else must set up a distinct API/developer account.
- 🚫 Never claim a chat subscription = an API key. Specifically: a ChatGPT Plus/Pro user and a Google AI Pro / Gemini Advanced user have no usable API key from that subscription — the UI must not imply otherwise.
As-of 2026-07-07. Provider billing structures change; OpenAI has periodically floated (but not shipped) subscription-linked API perks, and Google's free-tier limits tightened in April 2026. Re-verify each provider's "subscription includes API?" answer before shipping the copy above.
Caveat — as-of 2026-07-07, what's likely to change¶
- Prices drop fast. ElevenLabs already cut API + Music pricing up to 50% in 2026; Azure Neural HD fell $30→$22; assume all per-1M figures are ceilings, re-check before quoting to users.
- Music ownership/licensing is legally unsettled. Suno/Udio terms shifted mid-2026 after label deals (Warner/Suno) — ownership language keeps changing and copyright vesting is explicitly disclaimed. Re-verify any music provider's commercial terms at integration time and again before any "publish your podcast" feature ships.
- Model names churn. Chirp 3 HD, Sonic 3, Lyria 3, Aura-2, ElevenLabs Music v2,
gpt-4o-mini-ttsare current today; expect version bumps. Pin the model id in config, not code. - Local model licenses can flip. Piper already went MIT→GPL-3.0; XTTS weights are stranded by Coqui's shutdown. Prefer Apache-2.0 Kokoro for the bundled default specifically because its license is the least likely to bite.
- Verify official endpoints at build time — several exact paths/params above come from vendor docs that revision frequently; treat this doc as the map, not the final contract.