@neauoire @alderwick SO.
I tried using this other approach; writing the whole sequence to mem, and THEN playing it

https://pastebin.com/EvfqkSRW

problem is, if I try to set the sample length as #ffff (it's %BBTLEN), it doesn't play anything. but for example with #ffe0 works properly (just not creating/playing the entire melody) Not sure why.