(There's no video for Spotify yet. Please contribute to MR and add a video now!)
Spotify allows you to search and play millions of tracks, any time you like. Just search for it in Spotify, then play it.
Spotify-0-6-6-10.dmg (9.95 MiB / 10.44 MB)
Spotify v6.6.10 (last version for PPC) / DMG image
From Mac OS 10.4
Architecture: PPC (G4 or G5 recommended)
Emulating this? It should run fine under: QEMU