Complex sentence: As the trombone in its simplest form has neither crooks, valves nor keys to lower the pitch by a specific interval, trombonists use seven chromatic "slide positions", each of which progressively increases the length of the air column, thus lowering the pitch.
Split into simpler sentences: As the trombone in its simplest form has neither crooks, valves nor keys to lower the pitch by a specific interval, trombonists use seven chromatic "slide positions". Each position progressively increases the length of the air column, thus lowering the pitch.