I noticed that with my keyboard, if I hold down a note (a whole note will do for duration) I hear the GPO sample, plus I hear pulses. The pulses seem to correlate with the blinking light on my midi interface (USB Fast Track). I get this when using GPO as a standalone (K2 player) or as a plugin in Pro Tools.
I'm wondering if it's my keyboard. I have a Korg M1 (mint condition - I'm the original owner) that isn't a "true" midi controller. You have to put it in Global mode, go to page 10 on the display and selected your options. I've tried playing with local source on|off and clock local|external and still get the pulsation sounds with the sample. Other than the midi channel, that's about all I can control. Short duration notes like 1/8 to 1/4 don't have the pulsations.
I looked at the midi events list in Pro Tools and didn't see anything other than the notes.
Is this something someone else has seen? I'm going to try hauling my laptop over to a Sam Ash and see if they'll let me plug in an M-Audio keyboard controller to see if the problem goes away.
thanks in advance