Found another way to do it, with one block of inline ASM tricking the processor into giving up the Instruction Pointer (because apparently Intel thinks it's supposed to be a secret!) and pointing earlier in the block of ASM to some custom code that definitely has no function / subroutine / procedure hang-ups. 86box don't care. 86box just does not like my sound function... when it is called by a COM file. An EXE works fine. So, screw it, this compo's getting a COM version specific to DosBox-X.