Need help in trying to trace cause of distortion

Drywall emissions, couch out of phase, the fake Rembrandt generating negative clovid modulations, heart of pine permeating postulations of positive of sine waves.
Good luck with your mystery. Please inform once solved. 

One time that I will never forget was about an unidentified noise in some music but not all. It turned out to be a nearby lampshade emitting a sympathetic vibration from some of the music. Couldn't have guessed that one. My ears spoke to me that day.

With all the possibilities described here, this will be a daunting task!
May have to live with it as it seldom occurs.
But once it does, it’s crazy making!

Hi rvpiano
 it’s not a simple problem but if you do as someone else suggested, by elimination, you will be successful. My guess is similar to yours, I think it’s the speaker. Luckily, this one is the easiest to eliminate. Check to see if it does it with both. If not, move the speaker cables by swapping left for right. If the problem follows the cable, then you know it’s not the speaker. If the problem stays in that channel now it’s time to move the speakers to see whether the problem will follow the speaker. If it does, then you have your answer: it’s the speaker. If not, now do the same thing with the amps. Swap the input cables. If the problem follows the cable, it’s not the amp, move upstream. Hope that helps. 

RV, I think you are right and spenav 1++ Distortion like this is usually mechanical and the obvious culprit would be the driver that handles the midrange. It would only be in one speaker and just listening to each driver close up should be able to locate it. I assume you only use CDs so forget about miss tracking. I have seen cable connections do funny things, bad plugs or bad solder joints. First is to detect what channel has the problem as it is unlikely that both are doing exactly the same thing. If by chance both channels are involved the only common denominator would be the power supply of one of you electronic devices. If an amplification stage is not getting enough power it will clip early and there is a lot of energy at 1000 Hz but I think you would notice the distortion in loud passages and transients. Good Luck!