I'm trying to change the P-Switch's sound effect to the one from Super Mario Bros. 3 All-Stars from this pack: https://www.smwcentral.net/?p=section&a=details&id=18816
In AddMusicK I replaced the "global songs" .txt file number 6, the pswitch one, to the one from the custom sound pack.
When I get in game, the P Switch song is the correct one, the one from SMB3 All-Stars, but there is a weird volume fade in and out. The volume starts at a normal loudness, then goes a bit quiet, then goes louder again etc. until the P-Switch duration is over.
Here is a video showcasing the issue: https://www.youtube.com/watch?v=M43y_bjC86o&feature=youtu.be
I checked to see if all the samples were loaded with a "!" in the Addmusic_list.txt and they all are.
I am also using the SMB3 All-Stars fortress music during the level. This one works fine all throughout though.
I am using Higan emulator through RetroArch.
I managed to solve my issue after reasearching how music is stored in text files. My issue was actually in the text file I used. It contained some weird changes in volumes using the "qXX" code in the section where the music notes are written. I managed to correct the issue myself by editing the volume values of this code. The song now sounds like I want it to.