Sound RAM

403F	loopCount	incremented with each main loop (never used)
4040	v1Command	voice 1 command (0 for none)
4041	v1Init	voice 1 init flag (0 for needs-init)
4042	v2Command	voice 2 command (0 for none)
4043	v2Init	voice 2 init flag (0 for needs-init)
4044	v3Command	voice 3 command (0 for none)
4045	v3Init	voice 3 init flag (0 for needs-init)
4046	cmdRequest	requested command temporary for request processing
4047	m4047	never referenced
4048	m4048	never referenced
4049	v3priority	voice 3 priority temporary for request processing
404A	m404A	never referenced
404B	voiceNum	voice number (1,2, or 3)
404C	curEnable	current value of the AY enable register
404D	m404D	never referenced
404E	curFilter	current value of capacitor filters
405D	m405D
405E	m405E
4064	m4064
4065	m4065
4067	m4067
4110	m4110
4113	m4113
4130	m4130
4170	m4170
4171	m4171
4172	m4172
4173	m4173
4175	m4175
4176	m4176
4178	m4178
4180	m4180
4182	m4182
4184	m4184
41E4	m41E4
41E5	m41E5
41E7	m41E7
4280	m4280	set to 43 at start up (stack at 4044)
42A2	m42A2
42A3	m42A3
42A5	m42A5
42A6	m42A6
42B2	m42B2
42C2	m42C2
42C3	m42C3
42C4	m42C4
42C5	m42C5
42C8	m42C8

Stack pointer is initialized to 4400. It builds down from there.