Comment #20 on issue 1015 by [email protected]: doc line width http://code.google.com/p/lilypond/issues/detail?id=1015
That won't help. The only solution currently for snippets with instruments is to hand craft the line width. If the instrument is "violin" 15.5cm will likely be OK. If it's "reallylonginstrumentname" then it definitely won't. We could document the need to set line-width explicitly where a snippet has an instrument name. Alternatively we could launch an appeal for someone who understands spacing to fix issue 766 - it's probably one of the worst aspects of LilyPond's aesthetics that remains.
