CABROPL4 - NestorBASIC extension for direct control of OPL4
By Konami Man, 9-1998

How to use:

- Load it in any free segment, using NestorBASIC file access functions (refer 
to NestorBASIC manual). Note that load address must be equal to the address 
in which the code has been assembled (0 or #8000 for the supplied 
CABROPL4.BIN file, but you can assemble it in another address by just 
changing the ORG directive in the source code).

- Set input parameters (see below) and execute it with the NestorBASIC 
function 59 (user machine code routine execution): P(0)=Segment, P(1)=Address 
(0 or #8000 until you assemble source code in a different address), ?USR(59).

- 14 parameters can be set for each channel, and for only one channel at 
once; when you set the note parameter, you will cause the OPL4 to play it. 
Parameters 14 and 15 allows you to make up to 4 channels to play a note 
simultaneously.

Input parameters are as follows:

P(2)=Channel number (1-24)
P(3)=Parameter to be set
     0: OPL4 reset, no channel nor value set is necessary
     1: Instrument number (0-511)
	0-383 are ROM instruments, 384-511 are SRAM instruments
     2: Note (0-1023), makes OPL4 to play it
     3: Octave (-7 - 7)
     4: Volume (0-127)
     5: Stereo (-7 - 7)
     6: Vibrato (0-7)
     7: LFO speed (0-7)
     8: Tremolo (0-7)
     9: Pseudo reverb on/off/invert (1/0/-1)
    10: Channel on/off/invert (1/0/-1)
    11: Silences channel, no value set is necessary
    12: LFO reset, no value set is necessary
    13: OPL4 master volume (0-7), no channel set is necessary
P(4)=Value

If P(3)=14,
    P(8) to P(11) = Notes for channels 1 to 4, respectively
    P(7) = &B4321, 0 causes the channel to be silent (so &B1111 plays all 
channels, &B0011 only channels 1 and 2...)

If P(3)=15,
    P(4) to P(7)  = Channels A, B, C, D (1-24, 0=none)
    P(8) to P(11) = Notes for channels A, B, C, D