No, I doubt that's what is happening ... the command in question is the ENTER key from the remote, for which URC already has a command in their IR database. When I send an ENTER from the MX900 to the Denon (whether it's a single tap or press&hold), it behaves as expected.

For instance, in this case we're talking about the Denon 4306's iPod control ... when in iPod mode, sending a "tap" ENTER from MX900 _pauses_ playback, whereas a "press&hold" ENTER (again, from the MX900) _stops_ playback.

I suppose I could try to *learn* the extra-long IR command by pressing/holding the Denon remote while the MX is in learn mode, that may work ... even so, I would think there is a more elegant/flexible way to do this, by telling the MX editor to perform the press&hold itself?