I have a sung part which ought to accompany each one of my instrumental parts, as my (young) instrumentalists are to sometimes sing the melody, sometimes play their part. Some of the instruments are in Eb, others in Bb, some in C – you get the picture – and I want the sung part to transpose likewise.
The most practical way to do this would be to allow the sung part to follow the transpostion of the part it shares layout with. Or, even simpler, to be able to change transposition freely in both parts and score. That would make me able to notate «illegal» instruments like Horn in F#, etc., sometimes required by imaginative composers.
Maybe some of this is already possible? I couldn’t work it out – so I had to wotk around it instead, unfortunately.