Deezer vs Freesound

Deezer's REST API serves the catalog metadata behind the streaming app: tracks, albums, artists, playlists, charts, and full-text search. Unusually for a major streaming service its read endpoints are fully keyless — a plain GET against api.deezer.com returns real track data with no App ID, key, or token at all — while OAuth is reserved for endpoints that act on a user's own account, such as favorites or the activity feed. Responses can be requested as either JSON or XML via an output query parameter, and the API is free to use within Deezer's terms.

Freesound's APIv2 lets apps browse, search, and retrieve Freesound's library of user-uploaded sound clips — with content-based similarity search and audio-analysis features on top of plain metadata search — plus upload, comment, rate, and bookmark actions for authenticated users. It supports both token-based key auth and full OAuth2, defaults to JSON responses (XML and YAML are available but untested by the maintainers), and access is free for registered developers. The older APIv1 has reached end-of-life and is no longer available.