Hi Valentin, I came to the same conclusion as you: prefer \new Voice << { notes1 } { notes2 } >> over a series of chords. After I split the 2 voices, I was able to rebuild the original version like that so I could compare the notes to the original score before going further with my transcription.
Thank you for your proposed scheme script. However, although it does what was asked (extract voices), it is not really useful for my purpose of doing a transcription. I need a file with the notes because later, I will probably make some changes. Maybe I can use \displayLilyMusic for this and that would solve most of my problem but if I remember correctly, this only outputs absolute pitches. Is that true? Is there a way to output the music as relative? Thanks, F