Jack Behrens, Quarter-Tone Quartet, op. 20, mm. 1-2
Behrens uses a hybrid system in his quarter-tone string quartet. The first violin and viola are tuned to sound a quarter tone higher than normal, leaving the second violin and cello at regular pitch. The reversed noteheads indicate a pitch sounding on quarter tone higher than written. One thing that's not obvious from looking at the score is that the pizzicato notes in the viola sound a perfect octave above the altered notes in the cello.