Can’t seem to get the USB export to work, tried 2 different flash drives. Might have a go at debugging it at some point. You can see all the scripts used in the first 20 seconds of the video, I can try and explain them in detail if needed.
The “Turing Machine” implements an old but not usual algorithm based on a binary shift register, similar versions exist in the Noisering and the Buchla SoU, there is a good write up in it’s documentation.
Basically take a sequence of binary digits, rotate them on each clock pulse, and sometimes flip a bit. Convert the binary to decimal and output it as a voltage, the Turing Machine and it’s ilk do this in the analogue domain, they have their roots in analogue computing (as does all of our modular stuff…). It’s not that unrelated to the Orca algorithm.
E.g.
T = 0 : 00000001 = 1
T = 1 : 00000010 = 2
T = 2 : 00000100 = 4
T = 3 + flip: 00001001 = 9
You usually have non-deterministic control over whether the bit flips, so in effect you get an 8 step (for 8 bits) repeating sequence with a probability of the sequence evolving, if you keep the probability low then you end up with a slowly evolving sequence, it end ups being very musically, especially given the simplicity of the algorithm.
You can just about express the whole algorithm in a single Teletype script, first the setup:
P.N 0
P.START 0
P.L 8
L 0 7 : P I TOSS
i.e. set the pattern 0, to a length of 8, with randomised 0s and 1s.
Now for the script:
P.N 0
PROB 5 : P.PUSH EZ P.POP
P.INS 0 P.POP
X 0
L 0 4 : X ADD X LSH P I I
CV 1 N X
Use the same trigger for the script to trigger your envelope.
Breaking it down:
-
P.N 0
make sure we’re on pattern 0
-
PROB 5 : P.PUSH EZ P.POP
with a small probability, flip the last bit. A probability of 0 doesn’t flip any bits, but non-intuitively a probability of 100 doesn’t lead to a random sequence, instead, because we are flipping bits, it doubles the length of the sequence. A probability of 50 results in a random sequence.
-
P.INS 0 P.POP
rotate the bits (you can see this happening in the video on the tracker screen)
-
X 0
L 0 4 : X ADD X LSH P I I
this is the ‘cool’ bit, it’s a binary to decimal converter. In this case we’re only using the first 5 bits (= values between 0 and 31)
-
CV 1 N X
Output a note. Alternatively you can use the X value as an index into a scale, which is what I do in the video.
- View the tracker screen to see the bits rotate, hit the spacebar to manually flip the bit under the cursor.
The great thing about the Teletype is that it lets you easily fiddle with the algorithm, maybe you want to generate a second sequence related to the first somehow (maybe L 4 0 : X ADD X LSH P I I…?). Lots of possibilities.
