I get the best sounds IMO when I put ten concentric rings in each corner and another ten at two locations towards the middle, as shown in the picture:
Click ten times in exactly the same spot - be very careful not to move your mouse even one pixel! Then you will get rolling melodies occurring instead of just random notes...!
Putting circles right at the corners will ensure that you get a constant stream of bass notes. Then add circles to the center of the picture to get the melody going!
