This is the routine that plays a SFX;
This routine is used for the in game sound fx (like shooting) <<<<<<<<<<<<

In SCC-BLAFFER I use ONLY channel 3 for PSG (drums) channel 1 and 2 are unused.
What do I need to change in the routine below to let it leave channel 3 untouched ?

;+----- Set all PSG regs.-----+ ;SEE (Sound Effects Editor)
SETPSG:
    LD IX,PSGREG
    LD E,0      ;Start reg.0
    INC HL      ;[skip event byte]

;

    LD B,3      ;First 6 reg. [sound frequency]
STPS.0: PUSH BC
    LD C,(HL)   ;reg. $00, $02 or $04       -> Fine tune : A,B & C channels
    INC HL
    LD B,(HL)   ;reg. $01, $03 or $05       -> Coarse tune : A,B & C channels
    BIT 7,(HL)  ;check and handle Tuning
    CALL NZ,TUNWUP
    BIT 6,(HL)
    CALL NZ,TUNWDW
    INC HL
    LD A,C
    CALL WRTPSG
    LD A,B
    AND $0F
    CALL WRTPSG
    POP BC
    DJNZ STPS.0

    LD A,(HL)   ;reg. $06 [Rustle frequency]       -> Noise channel ?
    INC HL
    BIT 7,A
    CALL NZ,TUN_UP
    BIT 6,A
    CALL NZ,TUN_DW
    AND $1F
    CALL WRTPSG

    LD A,(HL)   ;reg. $07 [set channel ON/OFF]       ->Mixer :/EN noise /EN A /EN B /EN C
    AND $3F
    OR $80      ;set bit 7 is necessary to write the PSG!! ---> pour SSG/YM2610 : idem ??? pas sur !
    INC HL
    CALL WRTPSG

    LD B,3      ;reg.  $08-$0A [Volume  Channels A,B & C]
STPS.1: PUSH BC
    LD A,(HL)
    INC HL
    BIT 5,A
    JP NZ,STPS.2    ;Volume pattern is set.
    LD C,A
    AND $0F
    BIT 7,C
    CALL NZ,TUN_UP
    BIT 6,C
    CALL NZ,VOL_DW
    CALL FIXVOL ;                       Volume est param�trable !!
STPS.2: AND $1F
    CALL WRTPSG
    POP BC
    DJNZ STPS.1

    LD B,3      ; reg $0B-$0D [volume effect] ->Volume envelope period fine tune/coarse tune & Volume envelop shape
STPS_2: LD A,(HL)
    INC HL
    CALL WRTPSG
    DJNZ STPS_2
    RET


; Tuning
;- byte
TUN_UP: ADD A,(IX)  ; Up
    RET
TUN_DW: SUB (IX)    ; Down
    NEG
    RET
;- word
TUNWUP: PUSH HL
    LD L,(IX)
    LD H,(IX+1)
    ADD HL,BC
    PUSH HL
    POP BC
    POP HL
    RET
TUNWDW: PUSH HL
    LD L,(IX)
    LD H,(IX+1)
    XOR A
    SBC HL,BC
    PUSH HL
    POP BC
    POP HL
    RET

; Volume Down
VOL_DW: AND $0F
    LD B,A
    LD A,(IX+0)
    SUB B
    RET NC
    XOR A
    RET


; Make relative volume (depending on "SEEVOL"
; In: A, volume
; Out: A, new volume [seevol - (15-volume)]
FIXVOL: AND $0F
    LD B,A
    LD A,15
    SUB B
    LD C,A
    LD A,(SEEVOL)
    AND $0F
    SUB C
    RET NC
    XOR A
    RET


; Write PSG (not ROM-BIOS compatible!)
; In: A, data
; E, port
; IX, PSG store table
; Out: E+1
; IX+1
WRTPSG: LD (IX),A
    INC IX
    PUSH AF
    LD A,E
    OUT ($A0),A     ; pour MSX /port $A0(write) register Write port -> A modifier NEOGEO :OUT ($4),A
    INC E
    POP AF
    OUT ($A1),A     ; pour MSX /port $A1(write) Value Write port    -> A modifier NEOGEO :OUT ($5),A
    RET


;+----------------------------< Work Area >------------------------------------+
; reg. 0 1 2 3 4 5 6 7 8 9 A B C D
PSGREG: DB 0,0,0,0,0,0,0,0,0,0,0,0,0,0 ; - PSG port store buffer -