MusicXML: dynamics on one staff of a multi-staff part also show up on the other staff #2979

Is there an existing issue for this?

• I have searched the existing issues

I have read the contribution rules

• I have read CONTRIBUTING.md and, if any AI agent helped draft this issue, AGENTS.md.

AI authorship

AI-assisted (disclosure block included as described in AGENTS.md)

Current Behavior

When a MusicXML part has two staves (piano), a dynamic marking that is addressed to one staff via <staff> is applied to the other staff as well.

Using alphaTab's own test file 43e-Multistaff-ClefDynamics.xml from test-data/musicxml-testsuite: its description says the ffff and the wedge apply to only one voice or staff. Both <dynamics> directions (ffff, then p at an offset) are addressed to staff 1. Staff 2 has none.

After importing the file, reading beat.dynamics for every beat gives:

• Staff 1: FFFF for the first three beats of bar 1, then P from beat 4 onward.
• Staff 2: P on every beat, starting at bar 1 beat 1 (before the p appears on staff 1 at all).

So staff 2 carries the p that was written for staff 1, including on beats that come before it.

Expected Behavior

A dynamic addressed to staff 1 affects only staff 1. Staff 2 keeps the default dynamic until a mark addressed to staff 2 appears. This matches the test file's own description.

Steps To Reproduce

1. Load 43e-Multistaff-ClefDynamics.xml (from the alphaTab repo, packages/alphatab/test-data/musicxml-testsuite/) with the MusicXML importer.
2. Print beat.dynamics for each beat of both staves (staff 2 should stay at the default):

import * as alphaTab from '@coderline/alphatab';
import { readFileSync } from 'node:fs';

const score = alphaTab.importer.ScoreLoader.loadScoreFromBytes(
  new Uint8Array(readFileSync('43e-Multistaff-ClefDynamics.xml')),
  new alphaTab.Settings()
);
const names = Object.fromEntries(
  Object.entries(alphaTab.model.DynamicValue).filter(([, v]) => typeof v === 'number').map(([k, v]) => [v, k])
);
for (const staff of score.tracks[0].staves) {
  console.log('staff');
  staff.bars.forEach((bar, bi) =>
    bar.voices[0].beats.forEach((b, i) => console.log(`  bar ${bi + 1} beat ${i + 1}: ${names[b.dynamics]}`))
  );
}

Link to jsFiddle, CodePen, Project

No hosted project. The minimal script is inline under Steps To Reproduce and runs against the unmodified test file from this repo: https://github.com/CoderLine/alphaTab/blob/develop/packages/alphatab/test-data/musicxml-testsuite/43e-Multistaff-ClefDynamics.xml

Version and Environment

[AlphaTab][VersionInfo] alphaTab 1.9.0
[AlphaTab][VersionInfo] commit: c53d5adfcefd49af6c748fbadd5e054de8ce1b3c
[AlphaTab][VersionInfo] build date: 2026-10-29T06:11:56.958Z
[AlphaTab][VersionInfo] High DPI: 1
[AlphaTab][VersionInfo] Platform: NodeJs
[AlphaTab][VersionInfo] WebPack: false
[AlphaTab][VersionInfo] Vite: false
node v22.23.3 darwin arm64

The same result occurs with the published 1.9.0-alpha.1963.

Platform

Node.js

Anything else?

Fixing this would change how unmarked staves render in a number of existing visual reference tests (an unmarked staff would show the default f rather than a carried-over value), so I'm filing an issue first to ask which rendering the maintainers want before anyone writes a patch. Happy to prepare one once the direction is agreed.