On this subject of set vs override, if I want rehearsal marks to be
boxed letters and also want to use the letter I as a rehearsal
mark, how can I do that. Each set command overwrites the previous
value of the context property, so if I use:
\set Score.markFormatter = #format-mark-box-letters
\set Score.markFormatter = #format-mark-alphabet
then I get "I" as a rehearsal mark but the letters aren't boxed,
and if I use:
\set Score.markFormatter = #format-mark-alphabet
\set Score.markFormatter = #format-mark-box-letters