The LOCALPORT and GLOBALPORT just get numeric parameters (unit, port) and (voice, unit, port), respectively, which should be now quite intuitive as most of the time the port index is one of the parameters visible in the .asm file. Only a few units have extra ports beyond transformed variables. Overall, this should make the parsing of the .asm files a lot easier.
The stereo opcode variants have bit 1 of the command stream set. The polyphony is split into two parts: 1) polyphony, meaning that voices reuse the same opcodes; 2) multitrack voices, meaning that a track triggers more than voice. They both can be flexible defined in any combinations: for example voice 1 and 2 can be triggered by track 1 and use instrument 1, and voice 3 by track 2/instrument 2 and voice 4 by track 3/instrument 2. This is achieved through the use of bitmasks: in the aforementioned example, bit 1 of su_voicetrack_bitmask would be set, meaning "the voice after voice #1 will be triggered by the same track". On the other hand, bits 1 and 3 of su_polyphony_bitmask would be set to indicate that "the voices after #1 and #3 will reuse the same instruments".
