MuseScore 4.5.1 – Major bug when exporting separate audio tracks (solo/mute not respected, desync and cross-bleed)

🎻 MuseScore 4.5.1 – Major bug when exporting separate audio tracks (solo/mute not respected, desync and cross-bleed)

Platform: macOS
MuseScore version: 4.5.1
Audio engine: MuseSounds
File type: .mscz originally created in MuseScore 4.5.1
Problem type: export audio / solo-mute logic / desynchronization
Reproducible: Yes – always

❗️Bug summary:

When attempting to export audio from a MuseScore 4.5.1 project on every track all instruments are heard, even using either solo/mute in the mixer.- Other instruments are still heard, even when muted or when only one staff remains.

Then I tried to delete all but one staff, one by one, and the exported audio files consistently show the following issues:
- The export s desynchronizes, audio is inconsistent and differs from real-time playback.

🎯 Steps to reproduce:

1. Open a multi-staff score using MuseSounds.
2. Solo a single instrument in the mixer, or delete all other instruments from a copy of the score.
3. Export the audio (WAV, MP3, etc.)
4. Open the resulting file.

Expected:
- Only the soloed instrument is heard
- No desynchronization
- Clean and accurate audio matching what is played in the software

Actual:
- Other instruments bleed into the track
- Audio timing becomes unstable
- Dynamic and articulation changes may cause glitches

🧪 Additional notes:

• The same project exported cleanly from MuseScore Studio to an older version, 4.2.1 (after reimporting via MusicXML), after many attempts, (it refused to save the project), finally I could export correctly the audios from Musescore 4.2.1, bit it took more than 30 minutes (19 tracks, a piece of 5 minutes long).

• MuseScore Studio playback is musically excellent, but currently unusable for professional film work due to these export issues.

🙏 Request:

Please investigate this critical regression in the export engine. The ability to export clean, isolated audio tracks is essential for any professional use, especially in scoring, where syncing to film or DAW integration is required.

If you need a sample file to reproduce the bug, I can provide one.

Thank you for your work and for continuing to improve MuseScore Studio!