In anime at least there is a big difference between Vocals and BGM tracks. Forces, Tell Me Why, and Waiting So Long get credits because they have singers. The BGM for a show tends to be credited as a batch. For example they say that Jo Hisashi did the music for Mononoke Hime instead of saying who performed and what is this and that track called. That information can be found by buying an OST and comparing it to the TV series but a lot of times if a series has a lot of OSTs it can be hit or miss till you get the track you want.
So I guess a less provocative way of looking at the difference is Vocals vs. BGMs instead of songs versus music.
Oh... BGM is standing for Back Ground Music btw, since I forgot to mention that earlier.