how to - hear recording track with other recorded tracks

Having recorded a drum track through a Lexicon Alpha Desktop Recording Studio into Audacity, and being able to hear it in the speakers, how does one listen to the drum track and hear a new track, to record the new track while listening to the previously recorded, in this case, drum track?

Is it that the sound must get back to the Lexicon, to hear the two tracks simultaneously, and if this is so, how can that be accomplished? - tender bastard

Please see the pink panel at the top of this page. It’s much easier to help with device specifics if we know your operating system and version of Audacity.

Transport > Overdub which should be on by default.

And yes assuming Lexicon has a headphones output you should use that to monitor yourself and the Audacity track. Change the playback device in Device Toolbar to the Lexicon.