Slammer

A kick drum synthesizer. Three voices — SUB sine, MID sine+noise, TOP band-passed click — layered into a five-mode distortion palette, a tilt/low/notch master EQ, and a master bus that goes RMS comp → transformer drive → brickwall limiter → auto tube warmth. A parallel 909-style CLAP voice rides alongside. Sixteen-step sequencer, factory + user presets, one-shot WAV/AIFF bounce.

Free forever. Open source forever (GPL-3.0). Built because the kicks we liked cost $90 each and didn’t let us hear what was actually happening under the hood.

What’s here

• Three-layer kick engine — SUB sine with pitch envelope, MID sine+noise blend, TOP bandpass click transient. Independent tuning, amp + pitch envelopes, and drift per layer.
• 909-style CLAP voice — parallel, noise → 2-pole SVF bandpass → baked 3-burst + exponential tail. Tunable 500–5000 Hz, 50–400 ms tail. Bit-identical bypass when off.
• Five-voice distortion palette — Sat Clip (split-band rational), Sat Diode (asymmetric exponential), Sat Tape (drive-reactive LPF + hysteresis), Transformer drive (2nd+3rd harmonic blend with 60 Hz bloom), Master warmth (asymmetric cubic, auto-engages above 0 dB).
• Master bus compressor — three macros (Amount, Reaction, Transformer drive) plus a precision strip: Attack 0.3–50 ms, Release 20–800 ms, soft Knee 0–12 dB (Reiss & McPherson quadratic). Bit-identical hard-knee path at Knee = 0.
• Master EQ — tilt, low shelf, variable-Q notch.
• 16-step sequencer — host-synced in a DAW, internal transport standalone. Click or drag to paint.
• One-shot bounce — render the current sound through the full chain to 16-bit / 44.1 kHz WAV or AIFF. Offline, on the GUI thread, against a fresh DSP instance — bit-for-bit reproducible, and live audio keeps flowing during the render.
• Factory + user presets — forward-compatible JSON with #[serde(default)] on every field, so future versions don’t break your saves. Up/Down arrow keys cycle.
• Standalone + VST3 + CLAP for Linux, macOS (Apple Silicon + Intel), Windows.

What’s on purpose missing

• AU. The framework we built on (nih-plug) doesn’t support Apple’s AU format — it would mean rewriting from scratch in a different framework. So Logic Pro users: sorry, we can’t load in your DAW yet. Reaper, Bitwig, Live, Cubase, Studio One, FL, Renoise, and Ardour on Mac are all fine via VST3 or CLAP.
• Polyphony. It’s a kick drum. It’s monophonic on purpose.
• Free-form window resizing. The editor is a 680×444 rack panel with aspect-ratio-locked scaling — it snaps to integer multiples. Egui-baseview limitation, not a design choice.

Listen first

Ten one-shots bounced straight out of the plugin via the BOUNCE button — clean kicks, 808/909 emulations, claps, snares, toms, hats. No download, just hit play: hornfisk.github.io/slammer