For benchmarking and research purposes I created the following MIDI file:
It is panned fully to the left and has 127 Main Volume.
There are 101 notes, each 1 second long with 1 second between them.
For each note, Expression begins at 100 and goes down to 0.
A custom sample was created for this test by hand. It has default new-sample parameters except that there is no filter, the release time is 0, all effects are disabled, etc. It is included as an attachment to this post.
The resulting WAV file, exported directly to USB, is shown:
That’s an OS bug. You can get similar results by tapping a key over and over as well, so it is unrelated to the MIDI interface. Because of that, I can explain some of what you see there.
Sometimes with this sample you can release it and the sound continues to play but shifted and garbled somehow.
This is how it looks in the WAV file.
The sample plays regularly until release, then it goes silent for a few samples and then starts up again in a garbled way. This particular WAV file was created with MIDI playback precision, so it is not a matter of bouncing a finger on the keys etc.
When the next note plays, this garbled mess becomes one of 3 things:
#2: Quieter, as if the garble is cancelling out some of the samples from the note being held.
#3: Louder, as if the garble is adding to some of the samples of the note being held.
If my descriptions for how I created the performance and the MIDI are not enough, I can send the actual files. But all you need to do is load this sample, disable effects (reverb etc.) and tap the keyboard. I believe it had this issue with and without filters and with and without effects, but for reproduction purposes that is how I made the sound file. Otherwise the parameters are default and the note only plays at maximum velocity.
Firmware is 2.00.3.
I am not able to modify that at this time.