I have a Yamaha CP 88, connected via midi 5 pin cables, through the sound card and I have a Novation SL Mk III, connected via usb, directly to the computer. Issue : when I open a synth in all midi inputs mode, I get a “rumbling” sound of whatever sequencing or arpeggiating or modulating activity present in the opening preset. In time, the volume grows, like an infinite delay being filled with more and more information. After I choose a specific controller, everything goes back to normal. Maybe some midi that should be filtered or some midi clock going wild.
Hi and welcome to the forum,
To me it looks one of the devices sends unwanted MIDI data out. Just remove the unwanted MIDI Port from the list in the Studio >Studio Setup > MIDI Ports Setup, please.