Week 8, Lesson 2 - Binary patterns with struct, stitch and sew

Learning Tidalcycles course Week 8 - loads of lovely functions
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Here's a quick introduction to binary patterns, focussing on using them to switch between a pair of functions with stitch and sew.

-- Binary patterns

-- The patterns you send to SuperDirt tend to contain values of type
-- String (for words), Double (for decimal numbers) or Int (for whole
-- numbers). One pattern type you probably won't send to SuperDirt is
-- of type Bool - short for Boolean.

-- Boolean values can be either True or False. You've probably seen
-- then used with with 'struct', e.g.:

d1 $ struct "t f t t f t f f" $ sound "snare:4"

-- 'struct' provides structure for the pattern on the right; whenever
-- there's a 't' (i.e., a true value) in the boolean pattern, the
-- snare fires.

-- It works with euclidean syntax too:
d1 $ struct "t(3,8)" $ sound "snare:4"

-- The above creates a new pattern with three events per cycle,
-- according to a Euclidean pattern.

-- Lets have a look at that euclidean pattern:
drawLine $ struct "t(3,8)" "a"

-- So what do you think would happen if you changed that 't' (for
-- true) for an 'f' (for false)? Lets try:
drawLine $ struct "f(3,8)" "a"

-- Lets listen to that structure too:
d1 $ struct "f(3,8)" $ sound "snare:4"

-- You can see and hear that the *inverse* of the Euclidean pattern is
-- played. What was true, is now false, and vice-versa.. It's the
-- 'empty' steps which get the true values, and which we end up
-- hearing.

-- This is clearer if we play a t(3,8) against an inverted f(3,8):
d1 $ stack [struct "t(3,8)" $ sound "kick:4",
            struct "f(3,8)" $ sound "snare:4"
           ]

-- You can hear that the snares are 'filling in' where the kicks
-- aren't playing - they never play at the same time.

-- Filling in patterns like this is a lot of fun, and there's a
-- function called 'stitch' that makes it easier:
d1 $ stitch "t(3,8)" (sound "kick:4") (sound "snare:4")

-- You only have to give the boolean pattern once, 'stitch' takes care
-- of inverting the pattern for the second pattern. It's called
-- 'stitch', because it's like going up and down to stitch two things
-- together.

-- You can make more complicated boolean patterns to quickly get some
-- fun patterns going:
d1 $ stitch "t(<3 5>,8,<0 2 3>)" (sound "kick:4") (sound "hc")

d1 $ stitch "t(<3 5>,<8 8 8 6>,<0 2 4>)" (sound "kick:4") (sound "hc")

-- Actually it'd be less typing do the stitching _inside_ the sound
-- control pattern:
d1 $ sound (stitch "t(<3 5>,<8 8 8 6>,<0 2 4>)" "kick:4" "hc")

-- In the above, I only have to write 'sound' once, because the
-- 'stitch' is working on patterns of words, not patterns of sounds.

-- You can also alternate between patterns of true, and patterns of false
-- values:
drawLine $ struct "<t f>(3,8)" "a"

-- If you prefer you can use '1' or '0' instead of 't' and 'f', the
-- result is exactly the same:
drawLine $ struct "<1 0>(3,8)" "a"

d1 $ struct "<1 0>(3,8)" $ sound "clap"

-- You don't have to use the Euclidean syntax, you can just right them
-- out by hand:
d1 $ stitch "t f t t f f t f" (sound "kick:4") (sound "hc")

-- .. and use the usual mininotation syntax:
d1 $ stitch "t f t [t f]*2 f ~ t f" (sound "kick:4") (sound "hc")
  # room 0.2 # sz 0.8

-- With stitch, the rhythmic structure comes from the boolean
-- pattern. It has a synonym friend called 'sew', which instead
-- preserves the structure of the patterns it's sewing together.

-- Lets try it:
d1 $ sew "t f" (sound "kick") (sound "clap:4")

-- Oh! We only hear the kick. That's because the 'f' only switches to
-- the second pattern for the second half of the cycle, and no new
-- 'clap's happen then.

-- If we have four claps spread over the cycle, we hear the second two
-- of them:
d1 $ sew "t f" (sound "kick") (sound "clap:4*4")

-- Sew can be really nice for blending together two more complicated
-- patterns. Lets have a listen to them individually first:

d1 $ chunk 4 (hurry 2) $ n "0 .. 7" # sound "cpu"

d1 $ n "0 .. 7" # sound "cpu2" # speed 1.5 # squiz 2

-- And now sewn:
d1 $ sew (iter 4 "t f")
  (chunk 4 (hurry 2) $ n "0 .. 7" # sound "cpu")
  (n "0 .. 7" # sound "cpu2" # speed 1.5 # squiz 2)

-- In the above I have a really simple "t f" binary pattern, but use
-- 'iter 4' so that it shifts by a quarter every cycle.. So you get
-- different parts of the sewn patterns coming through.
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