Add some (particularly cheesy) drawing of a brace and clefs on the grand staff.

Add some (particularly cheesy) drawing of a brace and clefs on the grand staff.

This assumes the presence of the Gonville-26 and Gonville-Brace fonts, (by
Simon Tatham). Though it would be simple enough to change the code to use
any Lilypond-compatible font, (if the glyph selection were also update or
just fixed to lookup glyphs by name instead of hard-coding the index).