Fighting sound mismatches (1/2)

Some projects have sounded different since the Audiotool relaunch. We found problems in two places:

Parts of the new audio engine behaved differently from the legacy engine.
The conversion of legacy projects missed or changed some information.

We tackle these problems in two phases.

Today, we are tackling problem A and bringing playback closer to the legacy sound. In part 2, we’ll tackle problem B and reconvert eligible legacy projects using an updated converter.

Part 1: What changes today

These updates address specific causes of sound mismatches. They don’t make the two engines identical. Below, we explain what changes today, what you might hear, and where differences remain.

What today’s update means for your projects

Some fixes change how the engine interprets saved parameter values. We have updated project data alongside those fixes to preserve current playback where possible.

Some fixes still change how projects sound. That includes projects created since the relaunch, particularly if you used behavior that we’re now changing. Bringing older projects closer to their original sound can also affect music made with the newer behavior.

Empty automation regions: a change that may need your attention

Previously, an empty automation region reset its parameter to the value set on the device. The engine now treats an empty region as though it weren’t there.

If you used empty regions to reset a parameter, those passages may sound different. This was the biggest audible change identified during testing.

An empty Gain automation region on a track. The region contains no automation points. — An empty Gain automation region. The region contains no automation points.

How to fix a sound difference caused by an empty automation region.

To fix a passage that used an empty region as a reset:

Disable the automation lane.
Delete the empty automation region.
Create a new automation region and adjust its length.
Enable the automation lane.

We’re sorry for the extra work this creates. If you need help identifying the value or restoring the behavior, contact us on Discord or through the bug report form.

Other changes today

Automation display

We updated the UI behavior of the automation lanes for Orbit’s A/B filter frequencies and Stereo Enhancer’s Tone parameter. This change does not affect the sound.

A Tone automation lane before and after the update. The curve keeps its values but is now drawn with a different shape. — Stereo Enhancer’s Tone automation before and after the update. The curve keeps its values and is drawn with a different shape.

A Filter A Frequency automation lane before and after the update. The straight ramp is now drawn as a curve. — Orbit’s Filter A Frequency automation before and after the update. The straight ramp is now drawn as a curve.

Playback and device behavior

Pulsar tempo automation: The delay now responds to tempo changes more like the legacy engine. Some differences will remain: the legacy engine updated tempo at sixteenth-note intervals, while the new engine updates it every audio block of 128 frames.
Rasselbock Shuffle: We fixed the random generator used by Shuffle. The effect may sound different in current projects and should more closely match its behavior before the relaunch.
Stompbox Reverb: We changed its internal processing to more closely match the legacy engine. This changes the character of the reverb.
Stompbox Delay automation: We fixed how the delay parameter changes before its first automation region. You may hear a difference, especially at the beginning of a project.
Stompbox Delay stability: We fixed an internal issue that could trigger the circuit breaker in specific cases.
Stompbox Delay feedback: At 100% feedback in projects at 120 BPM, the repeats could go on forever. They now fade out correctly as in the legacy engine.
Pattern regions: Malconstructed legacy projects could contain pattern regions that point to patterns the device doesn’t have, which crashed the new audio engine. This is now fixed.
Machiniste pattern mute and exclusive: Pattern mute and exclusive toggles are now correctly reset when a pattern region ends. Before, a pattern region’s setting was kept beyond the region end.
Matrix Arpeggiator Hold: The Hold toggle now works. Previously, it had no effect.
Stompbox Gate automation: We fixed incorrect parameter changes during automation. Projects with extensive Gate automation may sound different.
Pulverisateur overlapping notes: We fixed how the instrument chooses which notes to stop when it reaches its voice limit. The new Pulverisateur still has more voices than the legacy version, so passages with many overlapping notes can still sound different.

What we tested and the limits

Our core evaluation consisted of systematically analyzing roughly 170 legacy tracks plus 180 test projects, created prior to the relaunch. For each track, we performed full-spectrum renders in both the legacy engine and the new audio engine, then compared the resulting spectrograms to identify structural discrepancies in both parameter conversion and audio processing.

Three stacked spectrograms of the same track: the legacy render, the new render, and their difference. The difference panel is mostly black. — Example of a spectral comparison between pre-conversion, post-reconversion, and the difference, with black representing no difference.

In addition, we subjected approximately 200 post-relaunch projects to automated audio regression testing to rigorously monitor parameter behavior across modern workflows.

We chose to prioritize the roughly four million projects created before the relaunch. As a result, our testing coverage is stronger for older projects than for music created since. These comparisons also don’t guarantee that today’s update leaves every current project sounding unchanged.

If your project sounds different and you are unsure how to fix it, please report it on Discord or through the bug report form. Include the project link, where the difference occurs, and what you hear. If you have an earlier render that demonstrates it, that helps too. We’ll investigate, listen to the before and after variant, and help you work out what changed.

Part 2: reconverting legacy projects

The original conversion missed Tonematrix groove assignments, dropped Matrix Arpeggiator pattern regions and note-input cables, and swapped Curve’s low- and high-shelf automation.

We corrected those conversion errors, and restored support for older Pulverisateur and Stompbox Reverb variants, along with legacy sample-groove behavior.

We have reconverted eligible projects from their legacy files. Part 2 explains the conversion fixes and how each project was handled. These are the rules we followed:

What you’ve done since the relaunch	What happens during reconversion
Changed the project and published	The project is left untouched.
Changed the project without publishing	We first make a copy that preserves the project exactly as it is before reconversion. The original is then replaced with the reconverted version.
Made no changes to the project	The original is replaced with the reconverted version.

The copy preserves the version before the fix; the original receives the fix. This also means people opening the original to remix it get the corrected conversion.

If you prefer the reconverted original, you can delete the copy. If you want to keep your later edits, you can continue with the copy and publish it as a new track, or transfer those edits back to the original. The edits are preserved, but bringing them together with the reconversion may require work.

Part 2 explains the conversion fixes, the older device and groove behaviors we’re preserving, and how to work with the two versions of a project.

Thank you all for your help and patience!