For example, say you select an individual note head and ask to change its pitch. This is partly what that old RobustIterator stuff was all about, although I'm not saying we need to go to those lengths. A reasonable editing paradigm for layers is to have a single layer selected at a given time, and for all edits on a staff will take place within that layer only. Non-selected layers could be grey or something.
Chords are sets of notes that share both start time and layer.
Music that originated in something like a MIDI file or played on a keyboard will often have multiple themes per track, without having them explicitly separated into layers. If a notator is asked to render a track that hasn't been annotated with layer hints, it should probably demand that the fuzzy annotation is done first. Copyright 1999-2001 Open Source Development Network. All rights reserved.