The Grab Bag tool is too complicated for me to explain completely at this point, but I'll describe one way to get interesting things out of it. Assuming you have a General MIDI synth, use the More menu button and invoke More->Fill All->GM drums(4b). You should see the cells of the grid fill with randomly generated drum patterns. Press the Walk toggle button, and it will start playing the cells of the grid, walking from one to the next. Press the Walk toggle button again to turn it off.

Do the same thing with More->Fill All->BS Riff(4b) and it will fill the cells with melodic patterns.

Put multiple Grab Bag tools on the screen and start them simultaneously. There are menu items to let you control the grid size, the starttime quantization, etc.

There is a value button at the top that lets you set the MIDI channel (except for drums). The slider on the left controls volume, and the slider on the right controls how many notes of each pattern are included.