A podcast breaks every rule legalizing music in webcasts. A song in a podcast is entirely interactive, skippable, replayable, seekable, playlistable, saveable.
Labels and bands have their hands full. Figuring out how to legalize (most) music in podcasts would be a lot of work, money, struggle, and time. There isn’t a lot to be gained.
Rights holders would probably say: if you want to do a music podcast, use an existing licensed platform like Spotify, YouTube, or Soundcloud. It’s true that this is not MP3, and that it doesn’t work on an iPod. But it works.
Podcast listeners want talk, not music.
That’s good, because pure-music podcasts are really hard to navigate in podcasting apps. The UX for finding the right thing is not there.
This is not to overlook killer music-oriented shows like Song Exploder or Afropop Worldwide, which are talk about music.
Podcasters who want to focus on music are going to have tough sledding getting music licensed and finding an audience. A wise one will use YouTube, Spotify/Deezer/Apple Music/etc, or Soundcloud.
The one place where there is traction is in dance music, especially for working out. But this is so unusual that it is the exception that proves the rule. And I’d guess these exist as one distribution platform among many; because the DJs have already created the sets for posting to Soundcloud, Mixcloud and YouTube.
So I am skeptical about music-oriented podcasts, though I’d prefer to be optimistic. I hope to be proven wrong.