Careful not to burn anything out... Though the C64 is pretty indestructible - I connected all kinds of things to the IO lines of it back in the day... And a few inadvisable cases of soldering things straight to the user port pins (I'm amazed I never destroyed any machines.... that way)

A tip is to turn off the screen during sampling and playback, as otherwise the video chip steals a lot of memory cycles.

You might then also be interested in this far more impressive playback with the C64:

https://brokenbytes.blogspot.com/2018/03/a-48khz-digital-mus...