Obviously it's not intended to group RhythmicStaves in GrandStaves.
The solution is to use ordinary StaffGroups and overriding the
systemStartDelimiter. Could be like this:
--- snip ---
\version "2.13.35"
\score {
\new StaffGroup
<<
\new StaffGroup = "group I"
Hello,
I'd like to engrave some percussion sections for separate players. The groups
have their name for player numbers, and the individual rhythmic staves indicate
names of instruments. However, even though I include the engraver, the file
attached doesn't generate group names into the pdf. I
