How can I add an anacrusis (pick-up bar with fewer notes than the time signature) at the start of a piece?

[XenonApps]

I am creating an app which renders a music score from a MusicXML file. I've managed to overcome most of the challenges this entails. However, I have not found any way to render an anacrusis in the first measure of a piece. It's also conventional to finish the piece with with fewer notes to balance the value of the anacrusis. In both cases I have not found a way to avoid the error which occurs due to the number of notes in the measure not matching the time signature. Has anyone found a way to do this except by padding the measures with rests to make up the value?

[sschmidTU]

You probably want soft voice mode, e.g.:

const voice = new VF.Voice({
        num_beats: 4,
        beat_value: 4
      }).setMode(VF.Voice.Mode.SOFT);

[XenonApps]

Thanks, that's just what I needed! 👍