Hydra Extension

Hydra
BPM Tools

Tempo control for Hydra, closer to how BPM is handled in VJ software: tap tempo, resync, BPM nudging, a draggable HUD, and beat-synced helpers.

View on GitHub

Quick Start

await loadScript("https://link.beatmelab.com/hydra-bpm-tools")

Intended for Hydra patches that need manual tempo control during rehearsal or performance.

Features

Tempo control for Hydra

The main purpose of the library is simple: make BPM control in Hydra behave more like visual tools used in VJ workflows, where tempo can be tapped, corrected, resynced, and adjusted directly while a patch is running.

Draggable BPM HUD

Displays the current BPM on screen and can be dragged to any position while you work.

Tap tempo

Sets tempo by tapping, which is often the fastest way to match external music or video.

Resync

Resets Hydra time so beat-driven modulation starts again from a clean point.

Keyboard shortcuts

Includes direct shortcuts for tempo control, resync, hush, HUD visibility, and BPM or rate changes.

Hush toggle

Lets you blank the output and restore it without removing the timing state.

Beat-synced helpers

Provides beats(), beatsTri(), curve(), and range() for tempo-based modulation.

Rate multipliers

Lets you halve or double timing quickly while keeping the underlying BPM available.

Userscript auto-load

Can be installed as a userscript so the tool loads automatically each time the Hydra editor opens.

Installation

Load the script into Hydra

The default entry point is a short loader URL that points to the jsDelivr asset. A direct jsDelivr link is also available if you prefer an explicit CDN path.

Quick Start

await loadScript("https://link.beatmelab.com/hydra-bpm-tools")

Direct jsDelivr URL

Versioned CDN path

await loadScript("https://cdn.jsdelivr.net/gh/beatmelab/hydra-bpm-tools@v2.0.0/hydra-bpm-tools.lib.js")

Keyboard Shortcuts

Default bindings

The default bindings are centered on Ctrl+Shift to keep them consistent with other Hydra keyboard shortcuts. All shortcuts use Ctrl+Shift plus one additional key.

Hydra BPM Tools keyboard shortcuts
Shortcut	Action
`Ctrl`+`Shift`+`T`	Tap tempo
`Ctrl`+`Shift`+`R`	Resync
`Ctrl`+`Shift`+`↑`/`↓`	Adjust BPM
`Ctrl`+`Shift`+`←`/`→`	Halve or double the rate multiplier
`Ctrl`+`Shift`+`B`	Toggle hush()
`Ctrl`+`Shift`+`Enter`	Run sketch (and clear hush state)
`Ctrl`+`Shift`+`J`	Toggle HUD visibility

Beat Envelopes

BPM-synced helper functions

These functions return values that move with the current BPM. In practice, they are used as inputs for Hydra parameters such as scale(), rotate(), color(), or any place where a beat-synced numeric value is useful.

Hydra BPM Tools beat envelope functions
Function	Output	Use
`beats(n)`	`1 → 0` over `n` beats	Decay-style modulation.
`beats_(n)`	`0 → 1` over `n` beats	Ramp-up motion.
`beatsTri(n)`	`1 → 0 → 1` over `n` beats	Cyclic up/down movement.
`beatsTri_(n)`	`0 → 1 → 0` over `n` beats	Same cycle, inverted phase.

`.curve(q)`

Changes the response curve of the envelope without changing its BPM sync. Use it when the movement should feel sharper, softer, or more eased.

beatsTri(2).curve(2)

`.range(min, max)`

Remaps the normalized envelope output to the numeric interval required by the patch. Use it when Hydra expects values outside the default 0..1 range.

beatsTri(2).range(1, 2)

These modifiers can be chained together, for example: beatsTri(2).curve(2).range(1, 2)

Why Use It

Main use case

Tap tempo in Hydra

Hydra does not provide direct BPM controls. You can change the bpm variable manually, but that is awkward during rehearsal or performance.

Resync when timing drifts

Even if you set the bpm variable in code, resyncing phase is still inconvenient. This matters when the tempo is correct but the modulation has drifted out of sync.

Nudge BPM while running

Small BPM adjustments can be made without stopping the patch or rewriting values by hand.

Use tempo directly in patches

The same BPM used for control can also drive modulation through the envelope helpers.

Userscript

Automatic injection option

If you want the tool available every time the Hydra editor opens, you can also install it as a userscript. With a userscript manager, the library loads automatically whenever the Hydra editor opens.

Install a userscript manager (such as Tampermonkey or Violentmonkey ) in your favorite browser.
Click the "Install Userscript" button. Your userscript manager will handle the installation.

Install Userscript

Internals

How it works internally

Under the hood, Hydra BPM Tools updates Hydra's internal BPM value and resyncs beat-driven motion by resetting Hydra's internal time variable.

Programmatic API

Public methods

The same controls are also available as methods if you want to change tempo or transport state from code.

hydraBpmTools.setBpm(140)
hydraBpmTools.getBpm()
hydraBpmTools.setRate(2)
hydraBpmTools.resync()
hydraBpmTools.toggleHudVisibility()
hydraBpmTools.toggleHush()

Open Source

License and attribution

GPL-3.0

Hydra BPM Tools is released under the GNU General Public License v3.0.

Attribution

The envelope API is adapted from hyper-hydra .

Repository

Browse source, issues, and releases on GitHub.