It can be difficult to define what stock music is and what it sounds like probably because it's a category of music marked more by function than by style. After all, stock music is used for a variety of purposes some of which are apparent (radio, television shows and commercials, movies) while other uses are more obscure (cinema pre-shows, promotional or workplace training videos, conference presentations). This variety makes it hard to define stock music's function. Perhaps a hasty, tentative definition could be “background music for needs requiring pre-recorded music , often on a fast and affordable basis.” (Digression: don't assume stock music and Muzak are the same thing; for more information about their similarities and differences, see here and the other posts under the “Muzak” tag.)
Musically, there's a lot to consider as well. Stock music libraries (as they are commonly called; “library” here is really just a synonym for “series”) are produced all over the world by both independent start-ups and multi-national media corporations. Geography can consequently have an impact on a library's content as much as target market and temporal concerns (see here for more about this latter-most factor). Beyond these (sometimes latent) influences, an individual library needs to consciously decide what kind of role it's going to take – is it going to be a generlised, multi-purpose library or a specialised, niche collection? Many companies offer one or more of each in an effort to widen their appeal and beef up their catalogue. And sometimes a collection puts out scores of releases and is looking for a new way to diversify their library without creating too much of an anomaly; it's at this juncture that the albums go from quite broad topics such as jazz, comedy, and cinematic, to a narrower focus such gospel, teen pop, or string quartet.
Once in a while, though, a library will make a bold or unexpected statement right from the start. You'd think, for instance, that a flugelhorn themed release would emerge later in a library's development, but clearly the people at Work Music Library had a different idea because their Moods for Flugelhorn is album numero uno (they are an Italian library...). Check out the cover:
While I don't know exactly how old the album is (production music libraries aren't always the greatest about including the publication date with their albums), I'm tempted to say it's a 1990s CD re-release of an 80s record because 1) that cover is so very very dated for that decade 2) the CD itself is at least 15-20 years old because the CD label. . .
. . .has seeped through to the back:
This renders the CD largely unplayable -- it still does sort of play, shuffling and hiccuping along for an unsettling, seizure-inducing effect -- but that's okay since the musical content isn't anything beyond typical big band with solo brass type of stuff; moody, flugelhorn kind of stuff. Then again it does seem a slight shame that we'll never get to properly audition the aural rendering of "Hanky-Panky" or..."Scylla"?