I own four MOXF keyboards. Three MOXF6 and one MOXF8.

I do a lot of MIDI recording and arranging of Songs.

Every one of the keyboards has displayed a similar behavior and I’d like to know how common it is BEFORE I make an attempt to reach Yamaha tech support as one of MOXF6s is still under warranty.

Out of the blue, after working on ANOTHER part entirely, I will come back to play the full mix, hit play and one channel is suddenly screaming at top volume! Not just somewhat “hotter” then I remember mixing it, but a sudden ear-drum popping level. I of course hit the main fader and shout an expletive. Then I select the offending Part and look over the channel strip. There is, of course, nothing to see. All the data settings, the Voice assignment, all exactly as I left them. 

If I were to hit Play again, it will continue doing it. What has SEEMED to work is the old, tried-and-true, method—toggle the Voice in and out and it usually goes away. But of course this whole series of events would be a terrible thing to inflict on an audience with the PA system at full blast. Luckily, it has NEVER happened at a gig and that may be just luck OR maybe it’s because there is “something” I’m doing while Mixing that sets off the madness. 

The most common Voices that it occurs with are the Bass Drum and the Snare Drum. Sometimes both at the same time which is an extra special treat! Runner-up culprit is Bass guitar. Again, maybe just coincidence but those three instruments are ALWAYS on channels 9, 10 and 11. Correlation without causation, who knows? 

If I have four MOXF’s and they ALL do this on occasion, I’m pretty certain it’s happening to other people. If you don’t mind taking a moment to respond, I’m curious to know how common it is, any theories as to what’s going on in side the MOXF—seems like a power supply issue, but the individual channel aspect is beyond my feeble electronic knowledge.

I have seen a not-so-subtle drop off in quality control on these keyboards. Two of them were purchased new-in-the-box within the last 18 months. I know they are long-since discontinued, which might explain the quality nose-dive, but a warranty is a warranty and if this glitch is as common as I suspect, I’d think Yamaha would be way ahead of me.