GRiDS - Chord-driven Synthwave Groovebox - Downloadable ROM (3.0.0B) - (08/01/2026)

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

Use at your own risk. GRiDS is homebrew software, provided as is with no warranty of any kind, and the author accepts no liability for damage to hardware or loss of data. It writes to your SD card only when you save; back up anything on that card you care about. It never writes to console firmware or settings, and only ever reads a slot-2 cart.

*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.