CLICK TO MAKE SOME MUSIC
Ok, so vertically you have a scale of tones. The squares across any row horizontally are all the same note, but different beats. So clicking multiple squares in the same column makes a chord as the notes are voiced simultaneously. You can make patterns of rhythm, syncopation and single note melodies by selecting squares across the rows which don’t correspond to the same column as another squares above or below. A perfect demonstration of why rhythm is the most important element in music.