Receipt

“he will start and end his solos with some real live audio, but steps on a boss line selector pedal, which switches back between live sound and the pre-recorded track.”

Danny Sapko, at 4:59 of “The most insane FAKE musician I've ever seen.” on Danny Sapko’s channel.

Around it

4:41 Secondly, he changes his solos ever so slightly from time to time, meaning they haven't always been exactly the same over the years.
4:47 There are parts of the recording that he's miming to that he'll swap in and out.
4:59 And lastly, he will start and end his solos with some real live audio, but steps on a boss line selector pedal, which switches back between live sound and the pre-recorded track.
5:09 Watch this example where he mimes along and then presses the pedal and hits the bass to make it look live at the end.
5:31 Here's another example.