Thanks for sharing, I also augment my work by writing and producing "stock music".

another term for this is "library" music. Meaning the compositions are part of a library that a tv/movie/radio/etc production company retains a blanket license for in order to use in their content. For example ESPN buys a license to use any track from a FirstCom (a UMG arm) Library, then they can use any song in FirstCom's library on their show for an agreed sync rate and the writer(s) of the music get a royalty from that use.

It's a way for production companies to get contemporary hi-quality music at a lower sync fee than say a chart-topping artist would require. Since usually these libraries are catalogued by very specific details and genres, it's easy for a music supervisor to find a track that gives a similar feel to a popular sound but is still original. By being part of a library (as a composer) your music is more likely to get licensed since it is already cleared by the publishers and production company. It is also nice for the composers because usually there is a fee for the recording and you retain writer credit and splits.

Personally I think it is a great way to practice good production habits on both the aesthetic-side and planning/logistics-side. You get a budget and a set of deliverables (say 3 songs in the style of 2000's southern rap) and a deadline and the rest is up to you to deliver. The more you do, the more royalties slowly start to trickle in over each PRO payment period and you get better at production in the process.

maybe i'll do a post on my experience with it if anyone is interested in trying it out.