GRiDS - Chord-driven Synthwave Groovebox - Downloadable ROM (1.0.1) - (07/26/2026)
GRiDS, a synthwave groovebox for the Nintendo DS
Chord-driven synthwave groovebox. Three synth voices, an 80s drum machine, zero samples.
A synthwave groovebox that runs on a Nintendo DS. Paraphonic pad, supersaw lead, sub bass and a synthesized 80s drum machine, tied together by a chord track that re-pitches the other voices as the progression moves. Stereo chorus, gated snares, kick-synced pump. MIDI in and out. No samples.
Three synth voices run in software on the DS's audio CPU. The PAD is a paraphonic chord engine: up to six detuned oscillators through one shared filter and one envelope, so chords swell as a block rather than per note. The LEAD stacks detuned saws in unison, with portamento glide. The BASS is saw or pulse plus a sub-oscillator through a resonant lowpass.
The drum machine is synthesized at boot from analog recipes. There are no samples. A pitch-dropping sine kick, a gated-reverb snare, band-shaped claps, pitch-swept toms, and a six-oscillator metal stack for hats and cymbals. Four kits, from clean to distorted, on an eight-lane grid with per-step accent, ghosts, ratchets and probability.
Room reverb is printed into each one-shot at bake time. The drums play on hardware sound channels that no live effect can reach, so baking is what makes a gated snare possible at all.
The chord track
- The chord lane is what separates GRiDS from a step sequencer. You sequence a progression with root, chord type and inversion per step, then lock the other voices to it.
- The lead snaps to the chord or the scale, so a written riff re-pitches as the progression moves.
- The bass follows the root. Write one repeated note, switch on WALK, and it becomes an arpeggio that re-voices at every chord change.
- The arpeggiator can voice the chord lane instead of held keys.
Change one chord and everything downstream follows it.
Effects
Stereo chorus. A pump that ducks the mix from the kick lane. A delay whose time is set in musical divisions and stays locked when you change tempo. Per-device drive.
Sequencer
Sixteen patterns of up to 32 steps, with per-step velocity, gate, ratchet, probability, TIE and SLIDE. Live and step recording. Four motion lanes per pattern for knob automation and p-locks, including the chord locks themselves. Swing stored per pattern. Song mode chains 64 slots with repeats, mutes and per-slot tempo overrides. Eight levels of undo.
MIDI
With an mDS-style slot-2 cart, GRiDS is three-part multitimbral: lead, bass, and a chord channel where a played note is read as a chord root, so the lock layer follows a keyboard the same way it follows the sequencer. Drums on channel 10. Clock in and out. Around thirty CCs mapped, with the on-screen controls tracking incoming values.
Feature bullets
- Three synth voices, paraphonic PAD, supersaw LEAD and sub BASS, synthesized on the DS
- Chord track that re-pitches the lead, re-roots the bass and voices the arpeggiator
- Eight-lane 80s drum machine, four kits, gated-reverb snares, no samples
- 32-step, 16-pattern sequencer with motion recording, p-locks, ratchets, probability and per-pattern swing
- 64-slot song mode with repeats, mutes and tempo overrides
- Stereo chorus, kick-synced pump, tempo-synced delay, per-device drive
- Three-part multitimbral MIDI with a chord channel, plus clock in and out
- Saves to SD in 16 whole-song slots, 8-level undo, one-press panic
Specifications
Nintendo DS, DS Lite, DSi or 3DS with a flashcart
`.nds` homebrew
32768 Hz stereo
SD card for saving, optional, runs without
mDS-style slot-2 cart, optional
Manual Here
*GRiDS is an original work. Not affiliated with, endorsed by, or derived from Roland, Sequential, Oberheim, Nintendo or any other manufacturer. No third-party samples, trademarks or trade dress are used. All synthesis is original and generated on the device.*
*Built with devkitARM. Includes calico (Zope Public License 2.1, copyright fincs and devkitPro), libfat (BSD 3-clause, copyright 2006 Michael "Chishm" Chisholm), libnds (zlib license) and newlib.