Infohashes, NZB pointers, deduplication, formats, and source health. Music only, like the index itself.
A music index does not need the music. It needs to know exactly where the music already is, and a forty character string is enough to say so.
AC/DC, AC-DC and ACDC are one band. Getting a database to agree is where most of the work in a music index actually goes.
Usenet holds an enormous amount of music, split into thousands of pieces across servers. An NZB is the map that puts it back together.
Lossless is not automatically the right answer for a radio station. What matters is what happens after your encoder gets hold of it.
The worst thing a radio station can broadcast is silence. Choosing music by source health is how you avoid it.