Interesting post!
I was briefly in touch with a well-established musicologist at a local University asking for just this. He was vaguely aware of library's existence, but noted that there were only a few papers written on it, to his knowledge. I find most articles generally get bogged down in explaining the concept of library music or the business aspect, without ever going very deep or saying anything too interesting to someone who already is 'initiated'.
Of some interest to me, Robert Fink of UCLA wrote a paper on library in 2000, that specifically uses
Network Production Music and their digital/website system as an example. He's very critical of their claim to have invented 'the industrial sound' - as a fun exercise, taking their cues identified as "bold industrial", he points out the fact that they are not exactly wholly original, tracing the 'sound' back to Beethoven:
You can find some books on film/multimedia music in general that touch on library - many of the same 'rules' apply, after all. There are also books on specific composers that worked in library - I believe there is some writing that touches on Bernard Herrmann's works in the
CBS EZ Cue Library, for instance. For Italy, much of what was released as library was originally composed for a specific film, radio or TV production, and books on specific composers might touch on the music in those productions, without framing it as library music.
A general issue, I find, is that "library music" as a whole is
waaay too expansive to fit properly in a single book. We're talking about a well-established industry that has existed and grown continuously since the silent film era. It would be very interesting for someone to write a book on library, but I think it would necessarily have to be limited to a specific era, area, company or composer for it to be possible.
- So where do you want to start?