Can't view two tracks in piano roll screen
I'm running LPX 10.6.1. Yesterday I could hold the command key down, select two tracks to view in the piano roll screen. Today, only one track comes up to view. Did I inadvertently disable some feature I'm not aware of? How can I view two tracks in piano roll editor again.
Thanks for your assistance.
Chris
MacBook Pro 13″, macOS 10.15