Hi, this came up in the german forum: https://lilypondforum.de/index.php/topic,1280.msg6613.html
A more minimel example: \version "2.24.2" %% \include "gregorian.ly" %% %% \layout { %% \context { %% \GregorianTranscriptionVoice %% \consists Stem_engraver %% \omit Stem %% } %% } \new GregorianTranscriptionStaff << \new GregorianTranscriptionVoice { \voiceOne b' } \new GregorianTranscriptionVoice { \voiceTwo g' } >> Returns: programming error: note-column has no direction { \voiceOne b' } Looks like its triggered by the removed Stem_engraver in 2.24., thus a first fix is to reconsist said engraver and omit Stems. Is this a valid bug? Thanks, Harm