101 lines
2.5 KiB
Markdown
101 lines
2.5 KiB
Markdown
# Timing with at
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Every step has a duration. By default, sounds emit at the very start of that duration. `at` changes *when* within the step sounds fire -- giving you sub-step rhythmic control without adding more steps.
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## The Basics
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`at` drains the entire stack and stores the values as timing offsets. Each value is a fraction of the step duration: 0 = start, 0.5 = halfway, 1.0 = next step boundary.
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```forth
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0.5 at kick s . ;; kick at the midpoint
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```
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Push multiple values before calling `at` to get multiple emits from a single `.`:
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```forth
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0 0.5 at kick s . ;; two kicks: one at start, one at midpoint
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0 0.25 0.5 0.75 at hat s . ;; four hats, evenly spaced
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```
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The deltas persist across multiple `.` calls until `clear` or a new `at`:
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```forth
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0 0.5 at
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kick s . ;; 2 kicks
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hat s . ;; 2 hats (same timing)
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clear
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snare s . ;; 1 snare (deltas cleared)
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```
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## Cross-product: at Without arp
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Without `arp`, deltas multiply with polyphonic voices. If you have 3 notes and 2 deltas, you get 6 emits -- every note at every delta:
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```forth
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0 0.5 at
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c4 e4 g4 note sine s . ;; 6 emits: 3 notes x 2 deltas
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```
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This is a chord played twice per step.
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## 1:1 Pairing: at With arp
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`arp` changes the behavior. Instead of cross-product, deltas and arp values pair up 1:1. Each delta gets one note from the arpeggio:
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```forth
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0 0.33 0.66 at
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c4 e4 g4 arp note sine s . ;; c4 at 0, e4 at 0.33, g4 at 0.66
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```
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If the lists differ in length, the shorter one wraps around:
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```forth
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0 0.25 0.5 0.75 at
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c4 e4 arp note sine s . ;; c4, e4, c4, e4 at 4 time points
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```
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This is THE key distinction. Without `arp`: every note at every time. With `arp`: one note per time slot.
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## Generating Deltas
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You rarely type deltas by hand. Use generators:
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Evenly spaced via `.,`:
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```forth
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0 1 0.25 ., at hat s . ;; 0 0.25 0.5 0.75 1.0
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```
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Euclidean distribution via `euclid`:
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```forth
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3 8 euclid at hat s . ;; 3 hats at positions 0, 3, 5
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```
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Random timing via `gen`:
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```forth
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{ 0.0 1.0 rand } 4 gen at hat s . ;; 4 hats at random positions
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```
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Geometric spacing via `geom..`:
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```forth
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0.0 2.0 4 geom.. at hat s . ;; exponentially spaced
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```
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## Gating at
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Wrap `at` expressions in quotations for conditional timing:
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```forth
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{ 0 0.25 0.5 0.75 at } 2 every ;; 16th-note hats every other bar
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hat s .
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{ 0 0.5 at } 0.5 chance ;; 50% chance of double-hit
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kick s .
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```
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When the quotation doesn't execute, no deltas are set -- you get the default single emit at beat start.
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