Conditionals

A common thing you’ll likely find yourself wanting to do is to not only play a random note (see the previous section on randomness) but also make a random decision and based on the outcome run some code or some other code. For example, you might want to randomly play a drum or a cymbal. We can achieve this with an if statement.

Flipping a Coin

So, let’s flip a coin: if it’s heads, play a drum, if it’s tails, play a cymbal. Easy. We can emulate a coin flip with our one_in function (introduced in the section on randomness) specifying a probability of 1 in 2: one_in(2). We can then use the result of this to decide between two pieces of code, the code to play the drum and the code to play the cymbal:

loop do

  if one_in(2)
    sample :drum_heavy_kick
  else
    sample :drum_cymbal_closed
  end
  
  sleep 0.5
  
end

Notice that if statements have three parts:

• The question to ask
• The first choice of code to run (if the answer to the question is yes)
• The second choice of code to run (if the answer to the question is no)

Typically in programming languages, the notion of yes is represented by the term true and the notion of no is represented by the term false. So we need to find a question that will give us a true or false answer which is exactly what one_in does.

Notice how the first choice is wrapped between the if and the else and the second choice is wrapped between the else and the end. Just like do/end blocks you can put multiple lines of code in either place. For example:

loop do

  if one_in(2)
    sample :drum_heavy_kick
    sleep 0.5
  else
    sample :drum_cymbal_closed
    sleep 0.25
  end
  
end

This time we’re sleeping for a different amount of time depending on which choice we make.

Simple if

Sometimes you want to optionally execute just one line of code. This is possible by placing if and then the question at the end. For example:

use_synth :dsaw

loop do
  play 50, amp: 0.3, release: 2
  play 53, amp: 0.3, release: 2 if one_in(2)
  play 57, amp: 0.3, release: 2 if one_in(3)
  play 60, amp: 0.3, release: 2 if one_in(4)
  sleep 1.5
end

This will play chords of different numbers with the chance of each note playing having a different probability.