MusicXML alter element imported into an accidental or ignored

Issue type

Import/export issue

Bug description

The MusicXML alter element is not imported verbatim into the note tuning.

As far as I can tell, the current behavior does the following:

• If the alter value corresponds to an existing accidental alteration value, the accidental is used
• If the alter value does not correspond to any accidental, it is ignored
• If an accidental is specified in the MusicXML, it is imported but the alter value is ignored

This behavior is confusing and ultimately incorrect, because it means that non-standard tunings cannot be imported from MusicXML. As a specification, MusicXML decouples the usage of the accidental (for display only) from the alter value (for playback).

Steps to reproduce

Examine the attached MusicXML score and observe the 3 cases mentioned in the description:

• Measure 1 E has an alter value of -0.5 and an accidental
• Measure 3 D has an alter value of +0.05
• Measure 3 E has an alter value of -0.15 and an accidental

On import:

• Measure 1 E is imported correctly
• Measure 3 D alter value is ignored
• Measure 3 E is imported with correct accidental but alter value is ignored and replaced with a MuseScore default

Screenshots/Screen recordings

No response

MuseScore Version

4.3.1-241490902, revision: github-musescore-musescore-026c26b

Regression

I don't know

Operating system

Pop!_OS 22.04 LTS

Additional context

No response

Start by importing the attached rast-tetrachord.zip MusicXML score and trace the MusicXML import handling for alter and accidental values. Done means non-standard alter values are preserved for playback independently of display accidentals, including the three reproduced cases.