# Lesson 20

# Counterpoint Lesson. In this lesson,
# we will look at ways to create
# counterpoint using Sonic Pi code.

# General Instructions:
#
# This lesson contains one example and
# one exercise (A).
#
# To listen to an example, change "comment"
# to "uncomment" on the "comment do" line,
# then click the "Run" menu command at the
# top of the Sonic Pi editor window.
# When you are done with the example, turn
# it off by changing "uncomment" back to
# "comment," and move on to the next section
# of the lesson.
#

# Example 1: Bach Invention No. 8.
# Notice the new commands "cue" and
# "sync." These allow you to synchronize
# the timing of separate threads.

comment do
  define :subject do | tonic |
    subject_a = [4, 7, 12]
    subject_b = [11, 9, 7, 9, 7, 5,
                 4, 5, 4, 2, 0]
    subject_c = [4, 7, 4, 12, 7]
    seq_a = [4, 7, 5, 7]
    seq_b = [0, 4, 2, 4]
    index = 0
    amplitude = 0.6
    3.times do
      play tonic, release: 0.25
      sleep 0.5
      play tonic + subject_a[index],
        release: 0.25, amp: amplitude
      index += 1
      amplitude += 0.2
      sleep 0.5
    end
    index = 0
    cue :start
    11.times do
      play tonic + subject_b[index],
        release: 0.4
      index += 1
      sleep 0.25
    end
    index = 0
    sleep 0.25
    5.times do
      play tonic + subject_c[index],
        release: 0.25
      index += 1
      sleep 0.5
    end
    3.times do
      index = 0
      amplitude = 1.2
      4.times do
        play tonic + 12 + seq_a[index],
          release: 0.4, amp: amplitude
        index += 1
        sleep 0.25
      end
    end
    3.times do
      index = 0
      amplitude = 0.7
      4.times do
        play tonic + 12 + seq_b[index],
          release: 0.4, amp: amplitude
        index += 1
        sleep 0.25
      end
    end
  end
  in_thread do
    subject :F4
  end
  in_thread do
    sync :start
    subject :F3
  end
end

# Exercise A:
# Example 1 plays the Invention No. 8
# through measure 6 (partially). Try to
# complete the code to play to the
# beginning of measure 12. Try
# restructuring the code so that
# repetitive musical patterns can be
# re-used.
#