(Not entirely sure this belongs here or under MBS/Web Service.)

In a normal release lookup that includes tracks, the "medium" entities have a "tracks" property, which is an array of the returned tracks. This seems like a perfectly sensible and consistent mapping (the media are "media", release events are "release-events", etc).

The same applies if you do a normal recording lookup that includes releases.

However, when doing a recording search, the result schema differs. In particular, the "medium" entities have a "track" property instead of "tracks". That seems like a bug (it's certainly annoying for a client library writer like me).