His father Karlo Aliev conducted an orchestra that was often heard on radio Sofia.
[1][2] At an early age Boris was already passionate about folk music, played first on the ocarina and later on the tambura in his father's orchestra.
[3] Here he acquired a feeling for the harmonic structure of Bulgarian music.
At the age of twelve, Karlov began to play the accordion, beginning with a simple 48-bass Hohner instrument, and progressing to a 120-bass.
[4] Based on generally short, simple, but fast musical phrases, frequently in the irregular rhythms that were originally played on traditional Bulgarian instruments such as the gaida (bagpipe) and kaval (end-blown flute), he innovated a rondo form where the special character of Bulgarian music nevertheless remained.