x Trigger Notation

In Roll You Own Syntax, I theorized how users could construct their own systems of notation using strings. I’ve constructed a working function, called trig(), to show how it’s done.

First, let’s see trig() in action. The following is complete conceptual prototype Slipmat program that generates a rock drum groove with 8th note hats:

#!/usr/bin/env slipmat

from JakeLib.Generators import trig
from EasyKit import hat, snare, kick
@trig('x.x. x.x. x.x. x.x.') hat()
@trig('.... x... .... x...') snare()
@trig('x... .... x... ....') kick()

This horizontal system for notating triggers, and others like it, can greatly improve the legibility of a piece, while catering to a composer’s preferred style of working. A composer quickly scans this and comprehends it without having to reconstruct it in their head from a list of individual events:

@0    hat()
@0    kick()
@0.5  hat()
@1    hat()
@1    snare()
@1.5  hat()
@2    hat()
@2    kick()
@2.5  hat()
@3    hat()
@3    snare()
@3.5  hat()

The form is lost in translation.

Building the function is pretty straight forward if you’re somewhat experienced with Python. I put together the following function definition, with docstrings, in roughly 15 minutes:

def trig(seq, res=0.25):
    Creates a numeric sequence from a string and returns a list.

    A string trigger sequencer, where an 'x' creates a trigger, and a
    '.' creates a rest. All other glyphs are ignored. The resolution
    of triggers and rests are determined by the argument res.

    seq -- A string containing a sequence of 'x' triggers and '.' rests
    res -- Resolution of note triggers and rests
    return -- A numeric list
    L = []  # The return list
    p = 0   # Position in sequence

    for c in seq:
        if c == 'x':
            L.append(p * res)
            p += 1            
        elif c == '.':
            p += 1

    return L

The trig() function accepts a string formatted in what I call ‘x trigger notation.’ The function parses the string and auto-generates a list of numbers representing trigger times. A trigger is denoted by an ‘x’, while a rest is a ‘.’. All other glyphs are ignored. I use a single space between beats for clarity. The default resolution is a 16th note, though trig() accepts an optional argument for changing the resolution, increasing its usefulness.

Import, Reuse, Remix

The best part about custom functions is that they can be reused multiple times in multiple programs by multiple people with the use of the import. No refactoring of code, no copy and paste, no reinventing of the wheel. Just import, reuse, remix.

Functions as Reusable Score Clips

I’m not a fan of the copy and paste method for composing computer music scores. I’d rather write something once, and reuse it as needed. Slipmat uses function definitions as one method for creating reusable score clips.

The following function rock_drums() stores a simple rock drum pattern with 8th note hats:

def rock_drums():
    @[0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5] hat()
    @[1, 3]                           snare()
    @[0, 2]                           kick()

Here, the rock_drum() clip is played 4 times:

@0  rock_drums()
@4  rock_drums()
@8  rock_drums()
@12 rock_drums()

Here are 16 bars using the range() shorthand method:

@range(0, 64, 4) rock_drums()

Using functions as clips can save time and keystrokes while greatly improving legibility. The easier your code is to read, the more likely others will remix your work. If they can’t make heads or tails out of it, they’re more likely to move on.

Custom Sequence List Generators

Python’s built-in range() list generator is full of possibilities when used in conjunction with Slipmat’s @ scheduler. And that’s just one generator out of, dare I say, a million possibilities.

Imagine being able to conveniently import generators from a massive user library of modules. This will be a reality for Slipmat for two reasons:

I built a list generator called range_plus(), which takes Python’s range() function a few steps farther. range() is limited to integers; range_plus() removes this restriction and allows for floats. range() supports a single increment step value; range_plus() additionally allows users to pass a list of increment step values that are chosen at random.

Here’s the working Python defintion for range_plus():

def range_plus(start, stop, random_steps=1):
    Returns a list of successive incremented values
    chosen randomly from a list.

    start -- Starting value
    stop --  End point
    random_steps -- A list of incremental values chosen at random or a
        single numeric value
    return -- A numeric list
    if stop < start:  # Avoid infinite loop from bad input
        return []

    if not isinstance(random_steps, list):
        random_steps = [random_steps]

    L = []

    while start < stop:
        start = start + random.choice(random_steps)

    return L

I made sure to write the docstrings, to make life easier for anyone who may import my code later. Here's a Python interpreter session to test out some numbers:

>>> from MyListGenerators import range_plus
>>> range_plus(0, 4, 0.5)
[0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5]
>>> range_plus(0, 4, [0.25, 0.25, 0.5, 0.75])
[0, 0.5, 1.0, 1.5, 1.75, 2.5, 3.0, 3.25, 3.75]

As applied to music, range_plus() would be a perfect fit for randomly generating rhythmic patterns, for things such as hi-hats.

@0  @range_plus(0, 4, [0.25, 0.25, 0.5, 0.75]) hat()
@4  @range_plus(0, 4, [0.25, 0.25, 0.5, 0.75]) hat()
@12 @range_plus(0, 4, [0.25, 0.25, 0.5, 0.75]) hat()
@16 @range_plus(0, 4, [0.25, 0.25, 0.5, 0.75]) hat()

Here's is one scenario for what those patterns would look like in trigger notation:

Bar 1:  x.x. x.xx ..x. xx.x
Bar 2:  xx.. x..x ..x. .xx.
Bar 3:  x..x ..x. xx.x .x..
Bar 4:  x.x. .xxx .xxx x..x

The 'x' is a 16th note trigger, the '.' is a 16th note rest, and spaces are used to distinguish between each quarter note.

Auto-Generating Lists

In yesterday’s blog, Lists as Micro-Sequencers, we discussed writing lists instead of individual events. Today, we’ll generate lists instead of writing list values.

Python comes with the built-in range() function that generates and returns a list of integers, which can be used to schedule events. The following python interpreter session demos range() with three sets of args along with their respective outputs.

>>> range(4)
[0, 1, 2, 3]
>>> range(5, 9)
[5, 6, 7, 8]
>>> range(0, 16, 4)
[0, 4, 8, 12]

The range() function can be a huge saver of time and keystrokes. Especially if you’re composing goa trance:

@range(1024) goa_kick()

“The kicks are done, man.” Just to be absolutely clear, that generates 1024 goa_kick() events, one per beat.