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The subtractive synth's amplitude-envelope release decremented at `(dt / r) * s` — the rate was multiplied by the sustain level, floored at 0.001. For any percussive patch (sustain≈0: Square Bass, Pulse Pluck, Noise Perc), release ran ~1000× too slow, so a 0.2 s tail took minutes. Since a voice's isActive follows its amp envelope, the voice never freed and kept rendering (3 osc + filter) indefinitely. That one bug produced all three reported symptoms: * missed note-offs / stuck notes needing panic — the note-off fires but the voice takes minutes to go silent, reading as ignored; * fast-tapping dropouts on every instrument — released-mid-envelope voices pile up (whole pool + 8 live audition voices) and CPU climbs until the audio callback overruns → xruns; * audition-then-play dropouts — audition notes are already stuck on the live pool before the sequencer stacks track voices on top. Release now ramps to zero at a constant 1/r rate, reaching silence within r seconds from any level (matching SampleVoice's behaviour). The Sampler/SoundFont path already captured its release rate at note-off, so it was less affected — but the shared synth voice pinned the CPU budget, which is why the stutter showed across all instruments. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Sizzletracker (Android)
A retro, grid-based music tracker for Android — monospace UI, pixel icons, demoscene-style pattern editing — playable equally with touch, keyboard, gamepad, and MIDI (USB or Bluetooth).
Features at a glance
- Tracker tab — 4-track pattern grid (note / velocity-hex / MIDI-channel per track), beat & bar coloring, tap-to-focus + drag-to-edit with haptics and scale-aware note entry; plus an 8-lane arrangement piano-roll (up to 256 bars) with A/B loop regions.
- Mix tab — 4 channels, each with an instrument + 4 FX slots, MIDI channel, volume, mute/solo.
- Toolbox tab — 16 slots for instruments (NES synth, sampler, SF2/XI) and effects (arp, transposer, LFO, tape delay, reverb, filters, 10-band EQ, bitcrusher). Every device has an auto-generated editor and text presets.
- Setup tab —
.sngproject save/load, color themes (with import/export), gamepad bindings, and searchable/collapsible MIDI bindings. - Master recording — render the master bus (with FX tail) to a WAV file.
- Background playback with a media notification (Play/Pause/Stop).
- Two-thread design — Compose UI on the main thread, a sample-accurate sound engine on its own high-priority thread.
There is also a standalone tools/samplepack-builder.html — an offline page for
assembling Sampler preset bundles (drop audio onto 16 note-labelled pads, then
download an importable .zip).
Build & run
Open the project in Android Studio (2024.1+) and Run on an API 26+ device or emulator.
From the CLI (the Gradle wrapper is committed, so a fresh clone needs no setup):
./gradlew assembleDebug
Where to start reading
See docs/DEVELOPER_HANDOVER.md — a from-scratch tour written for a developer new to Android: architecture, the file map, the "one action / one song / two threads" model, how to add an instrument or input, and an honest implemented-vs-TODO list.
Fastest orientation in code:
model/Project.kt → input/InputAction.kt → ui/AppViewModel.kt →
audio/AudioEngine.kt.
Project format
Songs use a human-readable .sng text format (see io/ProjectIo.kt), aligned in
spirit with the desktop
Sizzletracker; a byte-exact
compatibility shim is a listed TODO in the handover doc.
License
Sizzletracker is free software: you can redistribute it and/or modify it under
the terms of the GNU General Public License v3.0 or later
(GPL-3.0-or-later). See the LICENSE file for the full text; every
source file carries an SPDX GPL-3.0-or-later header.
Copyright © 2026 Reactorcoremeltdown