Changing the size of memory or changing the ROM version forces a reset of the PET.
The emulator has an IEEE-488 device at address 8. It can be used load and save (.prg) files.
Some programs don't run on ROM1 and some require more memory than the default 8K.
MUSIC! is a fun little program where you can play melodies on the PET keyboard, record them, and save them to tape or disk to play back laterk. The PET displays the notes you play on a musical staff drawn in PETSCII. As you play each note, the computer counts time and tries to make a reasonable guess at notating the rhythms you play.
The PETSCII notation is clever but ultimately the notes are ugly and that detracts from the overall aesthetic presentation of the program. While the timed note-entry feature is quite novel, it's hard to get the PET record precisely what you want to hear.