three‐quarter tone accidentals
Those of you who work with slippery-chicken and quarter tones know that only 1/4 tone accidentals and pitches are available, not 3/4 tone. This is mainly for the sake of simplicity: the fewer symbols we use, the more chance musicians have of being able to quickly assimilate our music. Another reason is that they're not strictly necessary: any 3/4 tone has a 1/4 tone enharmonic that usually suffices. However, in the rare cases when your music is somehow microtonally tonal (if you see what I mean), it does actually make sense to use 3/4 tone accidentals. Here's a piece I'm working on right now which is a case in point:
This is essentially a microtonal deviation from F# minor, so the 3/4 sharps make more sense than their enharmonic equivalents; they're also easier to read:
So how do we get 3/4 accidentals when slippery-chicken's pitch notation system doesn't support it? Well, by hacking into a pitch object slot. As the get-lp-data method for the pitch class uses the pitch's no-8ve slot in order to build up the string necessary to notate the pitch and its associated marks in Lilypond, we can set it to be the 3/4 accidental that Lilypond needs without affecting the fundamental structure of slippery-chicken or its pitch objects. Using Lilypond's English nomenclature for pitches we need the -tqs or -tqf accidental for 3/4 sharp or 3/4 flat, respectively.
Here's a bit of code that does this for the first 22 bars of my current piece, changing Aqf5 to Gtqs5 and Gqf5 to Ftqs on each occurrence:
(next-event +jitterbug+ 'solo nil t)
(loop for e = (next-event +jitterbug+ 'solo t nil 22)
for sym = (when e (get-pitch-symbol e))
for tqs = (case sym (aqf5 'gtqs) (gqf5 'ftqs))
while e do
(when tqs (setf (no-8ve (pitch-or-chord e)) tqs)))