GoatTracker

Using GoatTracker to Create F256K SID Music

This guide explains how to use GoatTracker to compose SID music and generate a packed .bin file that plays correctly on the F256K / F256K2 FPGA SID.

This document focuses on SID-only usage (no PSG or other sound chips).

---

1. Getting GoatTracker

• GoatTracker is available for Windows, macOS, and Linux.
• Download page: https://cadaver.github.io/
• The stereo version (useful for dual SIDs on F256K2) is available on SourceForge under the files tab.

---

2. Creating a Song

1. Create and edit your song in GoatTracker as you would for a C64.
2. Most instruments, effects, and patterns work correctly on the F256K FPGA SID.
3. GoatTracker was tuned for real C64 hardware, so FPGA SIDs may sound slightly different.

---

3. Pitch and Timing (Important)

Pitch and playback speed are related but separate settings.

• Playback speed is controlled by PAL vs NTSC timing (50 Hz vs 60 Hz).
• Pitch is controlled by the A-4 tuning value.

The F256K uses NTSC (60 Hz) timing so Goattracker must be configured accordingly.

---

3.1 Editing and Previewing on Your Computer

When composing music on your computer, use NTSC timing and corrected pitch.

Recommended settings:

goattracker -N -G424 song.sng

• -N — NTSC timing (60 Hz)
• -G424 — Correct pitch for NTSC preview

This setting is for editing only.

---

3.2 Packing for Playback on the F256K

The F256K requires a different tuning to produce true 440 Hz pitch.

Tested value:

• A-4 = 454 Hz

When packing a song, always start GoatTracker with the correct tuning and the song loaded at startup:

goattracker -G454 song.sng

Important: .sng files store tuning. Loading after startup will overwrite the setting and result in an incorrectly tuned packed file.

---

4. Packing the Song

Songs must be packed into a self-playing binary for use on the F256.

---

Option A: Internal Pack (F9)

• Press F9 in GoatTracker.
• Ensure it was started with -G454 and the song loaded.

The internal packer always uses the current tuning.

---

Option B: External Packer (GT2RELOC.EXE)

Recommended method.

Example command:

GT2RELOC song.sng song.bin -N -G454 -LD400 -Wa0 -Z80

---

Parameter Explanation

• song.sng — Input song
• song.bin — Output binary
• -N — NTSC timing
• -G454 — F256K tuning
• -LD400 — SID base address
• -Wa0 — Player load address ($A000)
• -Z80 — Zeropage ($80/$81)

---

Notes

• -Wxx sets the high byte only
  • Example:-Wa0 = $A000
• -Zxx specifies the starting zeropage address
  • uses two bytes
    • $80/$81 is tested and safe
    • Avoid $F0–$FF (kernel use)
• -Wxx and -Zxx are configurable based on your program's memory layout.

---

5. Playing the Music

---

5.1 Initialization

Call the music player's init routine once. It is located at the player load address (-Wxx).

JSR $A000  ; initialize song

---

5.2 Per-Frame Playback

Call the playback routine once per frame (SOF / 60 Hz).

• Playback routine address = init + 3

JSR $A003  ; play song for this frame

Repeat this call every frame for continuous playback.

---

6. Additional Notes

• Pitch and speed are not the same:
  • -N controls speed
  • -Gxx controls pitch
• GoatTracker adjusts pitch tables when switching PAL/NTSC, but manual A-4 correction is still required.
• The packed .bin file is unchanged between the C64 and the F256 - compatibility comes from correct timing, tuning, and memory placement.

---

Appendix: Minimal F256 SID Music Player Example

The following is a minimal working music player using kernel timers.

---

This example matches the configuration described in this wiki page:

• Player loaded at $A000 (-Wa0)
• Player routine at $A003
• Zeropage usage at $80/$81 (used internally by the player)
• NTSC / 60 Hz playback
  

; ============================================================================
; music_min.asm - Minimal Music Player for Wildbits/K & /Jr
; ============================================================================

   .cpu "65816"
   MMU_IO_CTRL = $01
   init_music = $A000
   play_music = init_music+3
   timer_cookie = $D0

*=$A0
   .dsection zp
   .cerror * > $AF, "Too many zero page variables"

   .include "api.asm"

   .section zp
   event: .dstruct kernel.event.event_t
   .send

*=$1000

start:
   stz MMU_IO_CTRL

   lda #<event
   sta kernel.args.events
   lda #>event
   sta kernel.args.events+1

   jsr init_music
   jsr SetTimer

loop:
   jsr handle_events
   bra loop

handle_events:
   lda kernel.args.events.pending
   bpl done_handle_events
   jsr kernel.NextEvent
   bcs done_handle_events
   jsr dispatch
   jmp handle_events

done_handle_events:
   rts

dispatch:
   lda event.type
   cmp #kernel.event.timer.EXPIRED
   beq music_playback
   rts

music_playback:
   jsr SetTimer
   jsr play_music
   rts

SetTimer:
   inc timer_cookie
   lda timer_cookie
   sta kernel.args.timer.absolute
   sta kernel.args.timer.cookie
   lda #kernel.args.timer.FRAMES
   sta kernel.args.timer.units
   jsr kernel.Clock.SetTimer
   rts

*=$A000
   .binary "testsong.bin"

---

Cheat Sheet

Edit / Preview (NTSC, correct pitch)

goattracker -N -G424 song.sng

Pack for F256K

GT2RELOC song.sng song.bin -N -G454 -LD400 -Wa0 -Z80

Internal Pack

goattracker -G454 song.sng

Press F9

---

Playback in your program

JSR $A000

JSR $A003

---

Tested Defaults for the F256

• SID: $D400
• Player: $A000
• Zeropage: $80/$81
• Timing: NTSC (60 Hz)

---

End of document.