SCI: SLATER: Hanging MIDI notes

[Thelypody]

ScummVM 2.9.0pre11296-g583660fb4cb (Apr 21 2025 14:44:13)
Windows 11 Enterprise 24H2 26100.3775
Game: Slater & Charlie Go Camping (DOS/English) (slater)

This game is an interactive storybook for young children. The story is accessed from the main menu by pressing either "READ TO ME" (autoplay mode) or "LET ME PLAY" (lets user switch pages themselves and interact with hotspots). During story, player can return to main menu by pressing a small red octagon with page number below the story picture.

Going between main menu and story pages has a chance of producing hanging music notes which don't get cleared properly. Going back and forth between screens can intensify these notes, producing unpleasant noise. It appears that the game uses only MIDI instruments 7-10 after the Sierra logo fanfare and instruments 7 and 8 can get stuck.

I've managed to reproduce this issue with audio device setting set to Windows MIDI ports and AdLib emulator. I couldn't reproduce it with MT-32 emulator, so maybe the MT32 driver used in this game does not suffer from the same issue.

[sluicebox]

Thanks for reporting this, I get the same results. I also tried on Mac with "Apple DLS Software Synthesizer" and get stuck notes. Confirmed that this does not occur in the original.

It seems like most any transition between pages can do this. Easiest to reproduce is going from page two to page three. The lowest note in the page two melody is held for a while so it's easy to anticipate it and click Next when it starts to get it stuck on page 3.

If I bring up the ScummVM menu with CTRL+F5, the music pauses and when I close the menu the music resumes without the stuck note.

This appears to have begun in ScummVM 1.8.0 in February 2016. The 1.7.0 release from July 2014 does not have stuck notes. Unfortunately I can't bisect it further, all my environments fail to build 2014-2016 source. Here are the commits with titles that include "SCI" and "MIDI" during that time frame, but they don't look relevant to SCI1.1:
134aa5af09053d88cd068b424b4e9b14e15d3df6 Oct 2 2014
165a8c26b9c47c056e679eb55ae9e73e15af2b14 Feb 15 2015
4f6f0fb148133df632104071185efa049c7d5fea Feb 18 2015

That SCI sound code has changed so much since then that I don't know if knowing the exact commit would even help much.

I don't know anything about SCI notes or sound drivers, just trying to narrow down some details for someone knowledgeable.

[sluicebox]

Steps to consistently reproduce:

1. Set audio device to Adlib emulator (default) or Windows MIDI or "Apple DLS Software Synthesizer"
2. Start game, click Let Me Play button in upper right
3. Wait for page one speech to complete, click Next arrow in lower right
4. Wait for page two speech to complete
5. Wait for page two music to play the low note in the melody that is held for a while and click Next. It's a short song so you can let it loop until you can anticipate the note, and then click next right when it starts. The page will transition while the note is still playing.
6. The note is stuck on page three.