Library music, also called production music, is recorded in advance and offered to broadcasters and film-makers through a catalogue, so that a producer can license a cue for a documentary, advert or news programme instead of commissioning a score or licensing a hit record. Albums were organised by mood or use, and composers often wrote to functional briefs for scenes that did not yet exist. Because libraries usually own all the rights, licensing tends to be straightforward.
De Wolfe set up what is often described as the first production music library in 1927, as sound arrived in cinema. The records of the 1960s and 1970s, from British libraries such as KPM, Bruton and Bosworth and composers such as Alan Hawkshaw, were mostly never sold in shops. Discarded by broadcasters and schools, they were rediscovered by collectors from the 1990s and later embraced by hip hop producers, partly because they are seen as simpler to clear than commercial releases. Their jazzy, funky and atmospheric cues fit naturally into the sample-based tradition from which lo-fi grew.