The "Polysynth" sound, with at least two staves, and a sufficiently long note, causes sound cracks

• Jul 9, 2017 - 13:17
Reported version
S4 - Minor

2.1 version 871c8ce/ Windows10

1) New score for two flutes -> Finish
( the test file is attached after step #5 )

2) In second flute: enter a D whole note, and hit "+" (for tie) one time

3) Skip the third measure -> enter again D whole note in measure 4, and hit "+" three times
(important, two times, and there is no more issue, unexpected but it is so. )

4) In top staff, measure 7, enter a sequence of 16th (with same note, D, important, too), let's say more or less three measures.

So, this configuration:

5) Hit F10 -> for second flute, change the sound: after click on the dropdown list, type Po, to get immediatly "Polysynth" sound

- The test file at this step: Polysynth.mscz

6) Close mixer, and Launch playback

Result: from measure 8, and next, you hear unpleasant sound cracks.


I observe the same behavior with 2.0.3.
It is different, or very attenuated (no really sound cracks) with the 2.0, 2.0.1 and 2.0.2

Nevertheless, listening attentively, there is a sound event in measure 8: a slight strident whistling on the second 16th, and a slight popping sound on the third 16th, and apparently nothing after)

So, I note two changes looking back:

- First change : the popping sound/strident whistling occurs with this Nightly, one June 18, 2014: d0768a7

After a first search, I note this commit the day before (any nightlies on June 17): at first sight, might be a good candidate? :…

To fix: #26381: Playback of supported ornaments incorrect if note is tied

- Second change, with severe sound cracks (which amplifies, multiplies the first issue?), appears on February 15, 2016 with this nightly: bc1a3a1

The previous nightly "works" (no sound cracks, by always of course popping sound): fe553bf

Maybe here ? :…

To fix (see comments #3, infinite loop test file, and #4, about polysynth instrument): #53696: Export as audio gets stuck at 99% with some file and some soundfont.

Hmm, it seems strange to me that my change involving ties would have had any relevance here, but I agree it sure looks that way. I will investigate.

I checked, and while the tie change triggered the problem in this case, it is not the cause. The cause is simply having a very long note with this particular sound - ties just happen to be one way of creating a long enough sound. But you can create the exact same situation by joining measures 4-7 into a single measure, and replacing the four tied whole notes with a single "longa" (the longest note value - looks like a breve with a stem, shortcut "9").

Title The "Polysynth" sound, with at least two staves, and a line of ties breaked, causes sound cracks The "Polysynth" sound, with at least two staves, and a sufficiently long note, causes sound cracks