you can use bgmplay"mml commands" and if you type mml it will give you a list of commands if you go to a certain page it will show you a list of instructions for changing the instrument. it says for @(numer to number)=(certain instruments you can check by looking at something or doing math after checking something)
not like that. heres an example of beep 0:BGMPLAY"T90:0(heres the instrument for beep 0)@256C1(a whole note 4 counts)
and there it will just do the beep 0. you can also do multiple notes, like this:BGMPLAY"T90:0@256CGFA#"
i hope this helped!