Note sounds for longer than specified length

[MiguelPescado]

I'm writing this because upon loading my project and soundfont to continue working on it from yesterday, one of my tracks (the Celesta) is not playing properly. The problem is that for some reason, the Celesta instrument will play out the full 1/4 note, no matter how short the note actually is and even if the Hold Pedal setting is set to 0. I checked to see if it was something I overlooked, so I loaded the song and soundfont into a different MIDI player, and the track had no issue playing the correct length of notes. My only guess is that a recent update may have inadvertently modified the code for the Celesta instrument, regarding how long the note should play.

[robertnhart]

Signal's synthesizer library was updated, perhaps that might be causing changes in how things sound.

You can access a preview version of Signal before the synthesizer update here:
https://signal-git-fix-cloud-song-ryohei-kameyamas-projects.vercel.app/edit

(This is the Preview link on this previous merge page: #576 )

If you could provide a minimal example MIDI file that sounds different in the old version and the current version of Signal, we might be better able to investigate.

If I understand you correctly, It seems like you are saying the audible duration of the note is not properly controlled by the specified duration of the note, it always sounds the same fixed duration despite what the specified duration of the note is. But in a quick test I did that doesn't seem to happen for me, so I guess there's some more details needed to recreate the problem.

Also, I'm confused if the hold pedal setting is important or not. The title "Celesta No Longer Works Properly With Hold Pedal" seems to suggest your problem only happens when the hold pedal is used, but you also said the problem happens "even if the Hold Pedal setting is set to 0" or off, suggesting the hold pedal setting is not relevant.

[MiguelPescado]

The link you sent me before the update seems to not have this issue, so now I'm just wondering what happened in the update to mess up this functionality.

To specify, I meant that the note still holds the same duration even if I manually set the Hold Pedal setting to 0. I initially thought that maybe leaving the setting off/blank was what was causing the issue, but it still happened either way.

I was also unsure if maybe the issue lies in the soundfont file I'm using, so I reloaded the song with a different soundfont, and the issue persisted. It was only when I changed back to the default soundfont that it was fixed, so now I'm thinking the problem lies in the update for signal loading any soundfont files besides its own default.

EDIT: It also seems I am unable to attach MIDI (.mid) files or SF2 (.sf2) files to this thread.

[robertnhart]

Status: We have discussed this some in the Discord channel #bug-reports starting at this message:

Moxxiconsin: [...] I'm recreating a track from SpongeBob SquarePants: SuperSponge (Playstation version) using [a] soundfont file [...] in the soundfont, the Celesta instrument is used as the "pitch-bent" version of the jazz guitar. Yesterday, the file sounded just fine, but in loading the file up on the new version of Signal, that instrument and that instrument only was messed up [...] forced to play out the entirety of the note.

(Note: GitHub user MiguelPescado is Discord user Moxxiconsin. GitHub user robertnhart is Discord user Bavi_H.)

The particular soundfont posted in the Discord discussion is exactly the same as the SuperSponge.sf2 file available here: SuperSponge (PSX) Soundfont.

In this soundfont, preset number 8 has following properties:

• It uses a sample with about 0.42 seconds before the looped portion begins.
• It has an "instrument" level volume envelope (delay-attack-hold-decay-sustain-release) with a hold portion of 0.5 seconds and with a long decay portion of about 2 or 3 seconds.

I made an example MIDI file that plays a very short note using this instrument sound.

• In my example MIDI file I used a 32nd note at 120 quarter notes per minute, so that's 0.0625 seconds of "note on" time.
• The version of Signal before the recent wavelet synthesizer update plays this note for about 0.0665 seconds, probably the entire "note on" time plus a small "release" time.
• The current version of Signal plays this note for about 0.510 seconds.

...

I've been looking over the SoundFont specification to learn how the volume envelope is supposed to work. It looks like when a "key off" happens, the synthesizer is supposed to immediately skip to the "release" part of the envelope, even if it hasn't yet reached the "sustain" part. I think the previous version of Signal probably did that, but the current verison might not be doing that.

I've been learning and investigating how volume envelopes specified in sf2 soundfonts are supposed to work, but it's getting complicated because when I test in other synthesizers, such as Synthesia, SynthFont, and MuseScore, they have different behaviors.

...

[robertnhart]

I previously said:

It looks like when a "key off" happens, the synthesizer is supposed to immediately skip to the "release" part of the envelope, even if it hasn't yet reached the "sustain" part. I think the previous version of Signal probably did that, but the current verison might not be doing that.

I found the part of the code that skips to the release part of the envelope, shown below. However, it looks like it was changed on purpose (not a mistake). So now I'm not certain if when a "key off" happens, the synthesizer is supposed to immediately skip to the "release" part of the envelope, even if it hasn't yet reached the "sustain" part is correct or not.

@ryohey , did you find any documents or synthesizers that support the behvior of always playing through the "attack" and "hold" phases before skipping to the "release" phase, even if a note off comes before the "attack" and "hold" phases are done? I'm trying to research how the volume envelope specified in an sf2 soundfont is supposed to work, but I'm having a hard time finding details about what should happen when a note off comes early (before the "sustain" phase).

Relevant code

In the wavelet file lib/src/processor/AmplitudeEnvelope.ts ...

In v0.7.4 from 2024-09-09, a Note Off skips to the release phase of the envelope:

  noteOff() {
    if (this.phase !== EnvelopePhase.forceStop) {
      this.phase = EnvelopePhase.release
    }
  }

In v0.7.6 from 2026-02-08, a Note Off only skips to the release phase when the current phase is decay or sustain, so the attack and hold are always played completely. (part one, part two):

  noteOff() {
    this.isNoteOff = true
  }

  calculateAmplitude(bufferSize: number): number {

    if (
      this.isNoteOff &&
      (this.phase === EnvelopePhase.decay ||
        this.phase === EnvelopePhase.sustain)
    ) {
      this.phase = EnvelopePhase.release
      this.decayLevel = this.lastAmplitude
    }

[MiguelPescado]

"In v0.7.6 from 2026-02-08, a Note Off only skips to the release phase when the current phase is decay or sustain, so the attack and hold are always played completely"

Does this mean that if I need to cut off the note, I have to use sustain and decay events? And if so, where and how do I implement them?

[ryohey]

@robertnhart Thank you very much for the thorough investigation, I really appreciate it as always.
According to SoundFont specification pages 47–48, “9.1.7 Envelope Generators”:

Whenever a key-off occurs, the envelope immediately enters a release phase during which the value linearly ramps from the current value to zero.

Based on this, I think the current implementation is incorrect and that we should revert to the previous one.

[robertnhart]

@MiguelPescado:

Does this mean that if I need to cut off the note, I have to use sustain and decay events? And if so, where and how do I implement them?

The terms attack, hold, decay, sustain, and release are descibing parts of a volume envelope. A volume envelope tells the synthesizer how to change the volume of a note when the note starts and when the note ends. For more details see below.

In Signal MIDI editor, you have no direct control over the volume envelope. Signal gets the various volume envelope values from the soundfont and uses those.

As a temporary workaround until Signal is fixed, my suggesion is to use the preview version of Signal before the synthesizer was updated.

...

More Details

Take a look at this graph of a volume envelope.

• In this graph, the horiztonal axis is time and the vertical axis is the volume level.
• The volume envelope begins at the time of the "key press", when the note starts. In the Signal Piano roll, this is the when the play position reaches the left edge of a note rectangle.
• After the note starts, there is an attack portion, where the volume of the note goes from zero to maximum.
• Then there can be a hold portion, where the volume stays at the maximum.
• Then there is a decay portion, where the volume goes from maximum down to the sustain level.
• The volume envelope will remain in the sustain portion until the "key release", the time when the "note ends". In the Signal Piano roll, this is when the play position reaches the right edge of a note rectangle.
• When the "key release" happens, the volume envelope goes to the release portion, where the volume goes down to zero.

Usually the attack time, hold time, and decay time are relatively short, so the note duration will usually be long enough for the volume envelope to get to the sustain part. But if the attack time, hold time, or decay time part of the envelope starts to get relatively long (or the note duration starts to get relatively short), it could happen that the volume envelope is not in the sustain part when the end of the note occurs. And this is happening in your example -- the particular sound you are using has a relatively long hold time and decay time specified in the soundfont.

What should the synthesizer do if the end of the note happens but the volume envelope is not yet at the sustain part?

• What Signal used to do, and what ryohey and I now both think it should be fixed to do again: When the end of the note is reached, the volume should start decreasing to zero again (the release portion) no matter if it has reached the sustain portion or is still in some ealier portion of the volume envelope.

• In the current version of Signal, it always plays out the attack and hold portion of the volume envelope to completion, so if the end of the note happens anywhere in the attack or hold portion, the release will have to wait until the end of the hold portion finishes.

[ryohey]

I recalled that this implementation was used to address the issue mentioned in #459 where the 0-tick drum doesn't sound. I'm not sure if it's possible to make the attack sound even if there's a note off with some other parameters that isn't supported by the wavelet.