One of the earliest examples of a Western composer using quarter tones in cello solo music is Ernest Bloch’s Schelomo, written in 1916. Bloch writes only one quartertone note in the entire piece, in the measure before rehearsal #36. As quartertone notation had not yet been widely used, he writes explicit instructions:
The highlighted text tranlates to “plus a 1/4-tone”, meaning a C quartertone sharp.
In 1975, Witold Lutoslawski composed Sacher Variation for Paul Sacher’s 70th birthday at the request of Mstislav Rostropovich. Lutoslawski constructed his piece using notes corresponding to the six letters of Sacher’s last name. One of the compelling motives of the piece is a rapid alternation between a pitch and its adjacent quartertone pitches. The first two lines are printed below:
The composer uses the three-quarter-flat notation , which leads to a very busy-looking page.
George Crumb achieves a wonderful effect in his landmark string quartet Black Angels (1970), in which, in the 13th movement entitled “Threnody III: Night of the Electric Insects,” he employs quartertone trills to create a terrifying chaotic buzzing.
The notation here is novel but effective: for the quarter-flats, Crumb uses a number “4” with a downward arrow:
British composer Michael Finnissy writes scores that look absolutely terrifying to play. Here are the first three systems from a piece for solo cello called Yalli (1981). As you can see it is chock full of quarter tones.