Monday, August 21, 2017

Modular Sequencing: 04 - And Gate Sequence

By combining short sequences with an and logic gate, complex and controlled rhythms can be created. Three interrelated patterns are created - the first sequence, the second sequence, and the points where both intersect against time and repetition.

With the assumption that both sequences are of different lengths, the resulting and logic will yield a rhythmic pattern that is longer than either. For example, take a rhythm that is eight steps long versus one that is only seven steps long. Fifty-six beats are required before the and logic rhythm will perform a perfect repetition.

A 40106-based oscillator is used to drive two 4022 counters. One counter has a loop length of the default eight counts. The other has a loop length of seven counts, which is achieved by connecting the Q7 output to the RES input. Selected Q output pins on the counters are connected via LEDs to the inputs of a 4081 and gate. The Q outputs that are selected form the rhythm of each loop. The selected outputs from the first counter are connected to the the first input of the 4081 gate. The selected outputs from the second counter are connected to the the second input of the 4081 gate. The resulting and logic will produce a rhythm formed from both counters. Three gate / trigger outputs are sent to the modular system - one output for the rhythm from the first counter, one output from the rhythm for the second counter, and the and logic rhythm.

Note that in this case, the LEDs are forming the rhythm, as there are no switches. By connecting the LEDs to different Q outputs on the counters, or by removing LEDs, the rhythm can be changed. By connecting the RES input to different Q outputs, rhythms of varying lengths from 2 - 7 beats can be achieved.

In this video example, the kick drum is from the first counter, the hi hat is from the second counter, and the tom is from the and logic.