# PumpFlow

A sidechain ducker: it ducks your sound in time with the beat, like a sidechained
compressor, without any routing.

## Overview

Put PumpFlow on a bassline, a pad or a whole bus. On every beat it pulls the volume down
and lets it swell back up, so the kick cuts through. Pick one of 16 curves, set how deep it
ducks with Mix, and drag the curve to make each duck shorter or longer to fit your kick.

## Controls

- **Mix**: how deep it ducks, 0 to 100%
- **Curves**: 16 shapes in five groups. Sidechain (8 shapes from fast to slow), Sub (slower,
  for sub bass), Trim (cuts the tail of a kick or a long sample), Reverse (pulls the sound
  away before the beat) and Rhythm (eighth-note pumps and a gate)
- **Slope**: drag left or right on the curve to make the duck shorter or longer
- **Shift**: the arrow buttons move the whole curve, a sixteenth of its length (outer) or
  1/256 (inner) at a time. Double-click the curve to reset Slope and Shift
- **Length**: 1/8, 1/4, 1/2 or a bar per cycle
- **Trigger**:
  - **Sync** follows your DAW's tempo and position, and keeps time while it's stopped
  - **MIDI** restarts the curve on every note, or on one note and channel
  - **Audio** restarts it on every hit in the sidechain input, so it follows kick patterns
    that aren't four to the floor. Without a sidechain it listens to its own input. It looks
    5 ms ahead (reported to your DAW as latency) so the duck lands exactly on the hit
    - **Sensitivity**: how readily a hit counts. Turn it up to catch quieter hits and hits
      over a ringing 808, down to skip ghost notes
    - **Kick only**: listens to the lows of each hit, so a drum bus or loop can be the
      sidechain without its snares and hats restarting the curve. It looks 20 ms ahead
      instead of 5 to tell them apart
  - **Dynamics** (MIDI and Audio): softer notes and hits duck less. MIDI goes by velocity,
    audio by each hit's level next to the loudest recent one
  - **Loop** (MIDI and Audio) repeats the curve until the next trigger. Off, the curve plays
    once and holds at the End marker, which you can drag
- **Band**: ducks only the frequencies below a crossover (20 Hz to 5.12 kHz), so the low end
  makes room for the kick while the rest of the sound carries on. The headphones button
  plays just that band
- **Ring mod**: ducks to the sidechain's own waveform as well, sample by sample, carving your
  sound around each cycle of the kick. It looks 5 ms ahead so each duck starts just before
  the peak. Turn Mix down to hear it without the curve, and turn on Band to carve only the
  lows. It needs a sidechain

The display shows the curve over one cycle with your sound drawn behind it as it plays, and
the sidechain's kick as a shape behind that, so you can line the slope up with it.

## System Requirements

- Windows 10 or later (64-bit), or macOS 10.15 or later on Apple silicon or Intel
- A host that loads VST3 plugins, or Audio Unit plugins on macOS

## Installation

Please refer to the Installation.txt file in the Documentation folder.

## Support & Updates

- Email: stvdwell@gmail.com
- Website: https://stvdwell.com/pumpflow/
- Support Development: https://ko-fi.com/stvdwell

## Version History

Version 1.1.0 (2026)
- Ring mod: ducks to each cycle of the sidechain's waveform, with look-ahead
- Dynamics: softer notes and hits duck less
- Sensitivity and Kick only for the audio trigger
- Projects from 1.0 sound the same

Version 1.0.0 (2026)
- Initial release
- The VST3 for Windows too

## License

Copyright (c) 2026 Anton Savytski (stvdwell). All rights reserved.
See LICENSE.txt for full terms and conditions. The fonts PumpFlow uses are under the
SIL Open Font License; see the Fonts folder. PumpFlow is built with JUCE and contains
open-source libraries, listed with their licences in Third-party licenses.txt.

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Created by Anton Savytski (stvdwell)
