Comment #18 on issue 2445 by [email protected]: Center a number above a measure http://code.google.com/p/lilypond/issues/detail?id=2445
define-event-class has been removed. It tampered with global variables and was unsuitable for multi-file runs. See input/regression/scheme-text-spanner.ly for how to do this now. This is actually a rather ad-hoc fix done instead of removing scheme-text-spanner altogether: the interface just builds upon somewhat sanitized internals, but the overall quality is not such that this would be dependable and/or cast in stone. It is still at a "meddling with internals" level of code quality, and thus not guaranteed to stick around and/or be supported by convert-ly.
Yes, this is not really satisfactory. But it will take some other work first before I can make progress here.
