Complex sentence: Haring's discography is difficult to trace, since many of the sides he performed on do not actually list his name, but several dozen sessions on which Haring led or arranged an orchestra have been catalogued by discographers, mostly falling between 1920 and 1931.
Split into simpler sentences: Haring's discography is difficult to trace, since many of the sides he performed on do not actually list his name. However, several dozen sessions on which Haring led or arranged an orchestra have been catalogued by discographers, mostly falling between 1920 and 1931.