Trying to catalogue my music collection has put me to thinking about ways music has changed over the years. The vast majority of popular music these days I am quite sure does not use the system of opus numbering found in Western classical music (and Wikipedia provides the term 'European art music', which for now I like so as not to have 'classical music' being ambiguous with the classical period, and intend to remember and use). Popular music these days does not use opus numbers (and why would it, being of a different music tradition?), but I have received the impression a rigorous such numbering was always unusual, and anyway I have also found it increasingly difficult to locate such catalogued numberings for composers from the end of the romantic period on. I do however often derive pleasure from playing about with cataloguing and classifying systems, applying them in unintended ways, and wonder at what results we might get attempting to give popular music opus numbers. To play at ordering by similar schemes and see if anything of diverting interest shows. Opus numbers, those seem a bit diverse in what they cover, since the signification seems to be 'chronological ordering of works released by %artist'. Covering single works, long or short, thematic collections or groups of pieces that happen to be released together. Seems fair for encompassing the variety of albums released these days as well. So what would we get then? Something like: Enya's Op. 17, No. 5 "Only If..." Or: The CROSS of Changes, Op. 2: III. Return to Innocence by Enigma The number is high for Enya because I attempted to count singles as separate releases, on the basis that those often feature additional versions of tracks and otherwise unavailable tracks as B-sides. For Enigma I did not bother, but probably should have reversed that since Enigma appears much more likely to release various remixes and cuts. Which means I took the easy approach there. I think this is nifty. It would amuse me greatly if I could do this with all the popular music in my collection and have an easy way of switching between music identity schemes.