Create 16th-century microtonal accidental

[Johannes Keller]

Hello!

I would like to use Lilypond for a critical edition of Nicola
Vicentino's treatise "L'antica musica" (Rome 1555). The original
notation uses an unconventional accidental to indicate a pitch
modification of a "Diesis" (ca. 1/5 of a whole tone). To mimic the
appearance of this sign I need to place a dot centered above the
notehead in the next available space (not above the staff like
articulations, not on staff lines).

I couldn't find a feature that detects the next available space. Do you
have recommendations how to implement such a behaviour?

Collisions with other noteheads (in chords), fingerings or articulations
wont' be an issue since the original notation never uses such things.

Examples of the original notation can be found here, see for example
fol. 12v (PDF p. 24):

http://vmirror.imslp.org/files/imglnks/usimg/9/94/IMSLP114662-PMLP210243-lantica_musica.pdf


Thank you!

Johannes