Here my code from nostaliga:
movei #DSP_start,r0
movei #DSP_RAM,r1
movei #(DSP_end-DSP_start),r2
nop
cpy_dsp:
load (r0),r3
addq #4,r0
subq #4,r2
store r3,(r1)
jr pl,cpy_dsp
addq #4,r1
movei #DSP_flag_replay_ON_OFF,r14
movei #song,r0
store r0,(r14+16)
movei #$100,r0
store r0,(r14+12)
movei #binPrecalcTable,r0
store r0,(r14+8)
movei #panning_table,r0
store r0,(r14+4)
moveq #0,r0
store r0,(r14)
and later
moveq #0,r0
bset #14,r0
movei #$f1a100,r14
store r0,(r14)
movei #$f1b000,r0
store r0,(r14+$10) ; PC
moveq #1,r0
store r0,(r14+$14) ; GO
BTW: Setting DSP_flag_replay_ON_OFF == 5 will pause the song. Setting it to 1 will stop the DSP (states 2 and 3 are internal, when 4 it is stopped)