Thanks again for your help. Yes, the first behavior you sent (single key between press & release) worked for play/pause.

Here's what I don't understand: when I go into Preferences>Behaviors>Button Mapping and select "Custom Actions" for the Play/Pause (A) button, I can create an action named "Play/Pause" and choose single key between press & release as well as other options. But when I do this and change these options, I see no effect. How did you get it to work? Do I need to go into the Behavior Construction Kit and create another MythFrontend behavior (in addition to the default one already in RB)?