It turns out that one particular issue that I have been looking into is not a problem with the patch, but a bug in the original VGA floppy version of Monkey Island 1. One particular variable is corrupted upon loading a saved game. This variable affects music in many scenes which will be lost until further corruption happens to restore the variable's original content. The corrupted variable gets stored in every saved game state.
Here's how to find out if your version is affected: run the game and go into the Scumm Bar. Save the game state. Exit to DOS, run the game again, load the game state you just saved. Exit the bar, skip the LeChuck cutscene, then enter the bar again. The bar music will be gone forever, unless further corruption restores the variable to a proper value. Saved game states that are affected may be fixed by opening SAVEGAME.* in a hex editor and changing the two bytes at 180C to 03 00 for AdLib or 04 00 for Roland.
According to my tests, VGA versions 1.0 and 1.1 using interpreter versions 5.0.15 and 5.0.18 (the error is in the interpreter, not the script code) are affected. The EGA (interpreter version 4.0.62) and CD-ROM versions do not seem to be affected.
Please try out the experiment described and post whether you can reproduce the problem. You can find out the interpreter version by running MONKEY /?. The patch would fix that problem as well; however, saved game states that include the corrupted variable would not be fixed. Of course, I could include a small .COM file that just repairs all SAVEGAME.* files in the directory ...