Thank you gluepet for your update
Hello,
Finally
I resolved the issue.

By default, the Keystep sends MIDI CC information, when either “REC” key (CC 50), or “PLAY/PAUSE” key (CC 54) or “STOP” key (CC 51) are pressed.
According to Prophet-6 user manual, Prophet-6 understands these MIDI CC as :
- CC 50 : Filter Env Attack
- CC 51 : Filter Env Decay
- CC 54 : High-pass Env Amount
This is why the sound changes as soon as one of they keys is pressed.
The solution is to set the Keystep stetting
“Transport Mode” to “OFF” with Arturia Midi Control Center software. This parameter is in the Transport Settings section.
Hope it can help.
