When I'm using MIDI for bass or keyboards and hit individual notes within either of those tracks, it also plays the drums.   This is not just recording.  If I just play bass on the MIDI keyboard, each note will also trigger a cymbal or something in drums.  Both the bass or keyboard note and drum play together.   I don't know what started it.   Does anyone have a solution?
 
Thanks,
Greg

This is because of how you have your MIDI channels setup - probably omni. So if you also have live input monitoring active on your drums track you will hear them too. Click the speaker icon to turn input monitoring off or assign different MIDI channels to each instrument.

I've never had this issue before.  And it just started.  I hadn't touched anything, and when I began to hit the keys for other instruments, drums were included.
I'll try your suggestions.
 
Thanks!
Greg

Also be aware that MIDI input "none" used to also mean omni, so the other (more effective) solution to recording in omni (your drums are probably set to omni, and I record this way myself) is to shut off input echo on tracks not being recorded or actively played (in your case drums).

The speaker icon was on.  I turned it off, and now it's fine.  Thanks for your help!
 
Greg

Yes, this is when the input echo is highlighted for more than one track. 
Another reason is if you have PVR open and the focus was on the drums. 
If PVR is open make sure to put focus on the track you are recording to.