MIDI tracks are recording an unwanted instrument sound

[Jen H]

This noob needs some help please!! My first MIDI track records beautifully using Pro Tools 7 LE, Digi 002, windows OS, and a YAMAHA DGX500 keyboard. However, when I record the 2nd track, I get additional notes of the first instrument on top of the desired instrument sound I'm intending to record on Track 2. For example, if my first track is a Piano sound, and my 2nd track is drums, the drum track ends up containing unwanted piano sounds on top of every note of the drums. After this happens, my YAMAHA keyboard itself also plays these unwanted dual sounds. If I turn my keyboard off and on again, it clears the problem and the keyboard notes sound true again (with no duplicate, dual instrument sounds), but I have not found a way to fix the Pro Tools recording issue. I should mention that this same exact system, set up, hardware, etc. worked beautifully for my about 5 years ago. I put it away for some time and I'm trying to get back into it now -- which required me to set up everything again from memory. Did I set something up wrong in terms of cables? Any help would be greatly appreciated!