type
  FSOUND_SAMPLE = record

    buff: Punsignedchar; // pointer to sound data
    ...
  end;
  PFSOUND_SAMPLE = ^FSOUND_SAMPLE;

  FSOUND_CHANNEL = record
    index: int; // position in channel pool.
    volume: int; // current volume (00-FFh).
    frequency: int; // speed or rate of playback in hz.
    pan: int; // panning value (00-FFh).
    actualvolume: int; // driver level current volume.
    actualpan: int; // driver level panning value.
    sampleoffset: unsignedint; // sample offset (sample starts playing from here).

    sptr: PFSOUND_SAMPLE; // currently playing sample

    ...
  end;

  PFSOUND_CHANNEL = ^FSOUND_CHANNEL;


procedure...
...
  asm
        push   ebp
        mov   ebx, mix_mixptr
        mov   mix_mixbuffptr, ebx

        mov   ecx, cptr
        mov   mix_cptr, ecx

        cmp   ecx, 0 // if (!cptr) ...
        je   @MixExit // ... then skip this channel!

>>>--> mov   ebx, [ecx+FSOUND_CHANNEL.sptr] // load the correct SAMPLE pointer
                                               // for this channel

        mov   mix_sptr, ebx // store sample pointer away
        cmp   ebx, 0 // if (!sptr) ...
        je   @MixExit // ... then skip this channel!

        // get pointer to sample buffer
        mov   eax, [ebx+FSOUND_SAMPLE.buff]
        mov   mix_samplebuff, eax
...