Motivation

As of now (version 8.1.0), it seems that bends (the technique of bending a string to make the note go higher, widely used in guitar for instance) can only be added as an articulation to notes with music21.articulations.FretBend.

In the doc, this articulation only has a number attribute which seems inherited from articulations.FretIndication while many more attributes are needed. Looking at the code, I see that some other attributes are mentioned though not documented nor actually used:

# in music21/articulations.py
class FretBend(FretIndication):
    bendAlter: interval.IntervalBase | None = None
    preBend: t.Any = None
    release: t.Any = None
    withBar: t.Any = None

These are the attributes used in musicXML (see the doc) which is great so I guess what's only missing is to actually implement them in the musicXML reader/writer?

edit: as a side note, I also wonder how Pitch should be managed when a note has a bend. For reading purposes, as it is done in musicXML, it probably makes more sense to keep the pitch of the note that has no bend. But for analysis, like in music21, a note with a bend should probably be considered as having the pitch of the destination of the bend, not the pitch of its starting point. This is an open discussion, I'd love to hear your thoughts on that.

Feature summary

• Complete the documentation on the FretBend articulation to mention all existing attributes (I can do this);
• Complete the class code to use the attributes, parse them from musicXML etc. (I could probably do it with some help);
• Change the class inheritance because a bend does not need to be a FretIndication, I think? Maybe a little complicated to change that and not that useful, I don't know;
• Make bends interact nicely between tablature staves and standard staves, see following example from GuitarPro for instance. I have no idea how to implement it, probably the hardest thing to do but it would be nice that a bend in a tablature staff automatically shows the corresponding pitch change on the related staff. This is also kinda related to the discussion on the pitch given to a note with a bend (see edit above).
  

Proposed implementation

To discuss

Intent

[x] I plan on implementing this myself.
[ ] I am willing to pay to have this feature added.
[x] I am starting a discussion with the hope that community members will volunteer their time to create this. I understand that individuals work on features of interest to them and that this feature may never be implemented.