Here's a solution:
. "${TM_SUPPORT_PATH}/lib/bash_init.sh" "$TM_LILYPOND" "$TM_FILENAME" 2>&1 | pre
1) In TM2, bash_init.sh needs to be loaded? 2) In TM2, stdout and stderr are differentiated? (Lilypond writes to stderr, so combining it before the pipe to pre works. Wasn't needed, apparently, on TM1.5)
If anyone has better information or fix, please share.
Thanks! Charles