Hi Mem,
The following are the terminologies I am using to describe the cube
column--refers to an arrangement of 3 LEDs if you are looking "down" on it from the top.
layer--refers to a 3x3 grid that is parallel to the surface on which the base of the cube is resting on
plane-- refers to an area that is PERPENDICULAR to the layer and comprises of 3 columns with LEDs from each layer. Think of a 3x3 grid but that is perpendicular to the base of the cube. In this way, a 3x3x3 cube has 3 vertical planes.
I think I will need 12 pins. 3 for 3 layers and 9 for 9 columns. It's like turn on the layer, then the column--you get 1 LED lit up. The problem I am having is : I can do what the instructables site shows me for an arrangement like that, but NOT for the cube. The architecture of the cube makes it difficult to do what the site shows.
I have the cube that is working properly --by working properly, I mean I have transistors properly connected and I can turn on a single LED, produce some basic patterns, but unfortunately, I have not been able to make each PLANE respond to music.