The Virtual Music Instrumentsoftware is designed to play prerecorded musical samples when the person waves a hand or tilts their head, activating symbols on the screen.
Ableton will have automatically loaded a pitched instrument in the software, and making this the center of Push's attention is just a button click (or two) away.
With dual mic and dual instrument inputs, he can sing and play at the same time for some multi-track recording, but the Toneport's real strength comes from its included software that models different mic, instrument and amp types to create a whole new sound from the low-cost setup.
You generally play a software synth using an external music keyboard plugged into the Mac via some variety of MIDI (Musical Instrument Digital Interface) hardware device for connecting electronic musical instruments to each other and to computers.