# A stock Game Boy Advance becomes a synth, no mods

Load custom software straight into a GBA's RAM over a link cable and the untouched handheld turns into a chiptune synthesizer.

- Category: Hardware (build)
- Device: [Game Boy Advance](https://afterware.xyz/d/game-boy-advance)
- Made by: [Andy](https://hackaday.com/2026/10/23/using-an-unmodded-gba-as-a-music-synth/) on Hackaday
- Original: https://computer.musicthing.co.uk/programs/108-gba/
- On Afterware: https://afterware.xyz/p/a-stock-game-boy-advance-becomes-a-synth-no-mods

## Can I build this?

- Difficulty: Intermediate
- AI-buildability: 4/5 (The work is mostly GBA homebrew code (sound registers, multiboot, input handling), which AI can write, but you still need a way to connect the GBA to a computer and get the multiboot transfer working.)
- Time: A weekend
- Cost: $30–60
- Parts: Game Boy Advance
- Tools: link cable, computer

Estimates based on the original write-up. How the AI-buildability score works: https://afterware.xyz/ai-buildability

## Build sheet

- Device: Game Boy Advance, unmodified
- Method: Multiboot over link cable
- Audio out: Headphone jack

## Starter prompt

```
Based on "A stock Game Boy Advance becomes a synth, no mods" on Afterware: https://afterware.xyz/p/a-stock-game-boy-advance-becomes-a-synth-no-mods

Write a multiboot-loadable GBA synthesizer program that runs from RAM when a Game Boy Advance is powered on via a link cable from a PC. Use the GBA's audio registers to generate square and noise channels, map the d-pad and A/B buttons to note and parameter control, and send audio out the headphone jack. Include a small PC-side loader script that transfers the binary over the link cable.
```

## Story

The GBA never gets opened. No soldering iron, no swapped chips, no yanked audio circuitry. The trick is the console's multiboot feature, built so one GBA could send game code over a link cable to a friend's console without a cartridge. That same door is open to anyone who wants to push their own program into the console's RAM.

The setup is simple. The GBA is connected to a computer, the synth software starts there, and when the handheld is powered on the synthesizer loads itself into memory. Sound comes out of the headphone jack, and controls are split between the computer and the console. The source shows the stock console working alongside other musical hardware, with sounds it calls impressive.

For anyone who wants into chiptune without pulling apart an original Sega Genesis for its sound chip, this is the cheap way in. You need a GBA, a link cable and a computer.

## Resources

- [GBA synthesizer program page](https://computer.musicthing.co.uk/programs/108-gba/)

Tags: game boy advance, chiptune, multiboot, link cable, synth, retro audio

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