Function make_all_variants_replacements 

pub fn make_all_variants_replacements(
    stream: &Stream,
    recurse: bool,
) -> Result<Stream>

Makes each variant of a copy of a stream that only inserts or only deletes into one that replaces: an insertion at the start, or a deletion anywhere but the end, takes in the element after it, and the others the element before it, moving back to start there: music21’s makeAllVariantsReplacements. With recurse, the variants of the streams the stream holds are made so, and not the stream’s own, as music21 does; music21’s variantNames leaves every variant as it is, so it is not taken.

Errors

A variant with no element before it to take in, or one that cannot say what it replaces.