# Lesson 12

# Arrays Lesson - Part 2. In this lesson,
# you will learn about arrays of arrays
# (multi-dimensional arrays) and rings.

# General Instructions:
#
# This lesson contains two examples and
# two exercises (A, B).
#
# 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.
#

# Arrays can hold any kind of object,
# including other arrays. This can be very
# useful for musical programming.

# Example 1: Multi-dimensional Array.

comment do
  triads_array = [[:C4, :E4, :G4],
                 [:F4, :A4, :C5],
                 [:G4, :B4, :D5]]
  count = triads_array.length
  index = 0
  count.times do
    triad_array = triads_array[index]
    t_count = triad_array.length
    t_index = 0
    t_count.times do
      note = triad_array[t_index]
      play note
      sleep 1
      t_index += 1
    end
    index += 1
  end
end

# Exercise A
# 1) Change the name and contents of the
#    triads_array in Example 1
#    to the following:

#   a) seventh_chord_array (V7 chords in C, F,
#      and G Major)
#   b) interval_array (M2, M3, P4, P5, M6, M7, P8)
#   c) rhythms_array (Pie, Apple, Huckleberry,
#      Blackberry, Butterscotch)

# 2) For a) and b), change the name of
#    triad_array in the inner loop to match
#    the changed triads_array.
#    For c), choose a note to play, and
#    use the sleep command to create a rhythm
#    based on each value in each rhythm array
#    retrieved from the rhythms_array. Change
#    the name of triad_array to rhythm_array.
#    Try moving the sleep 1 command for a) so
#    that each 7th chord plays harmonically
#    as a block rather than as a broken chord.

# Sonic Pi has a type of array called a ring
# that is circular. The index of a ring is not
# limited to the number of values in the ring
# as it is in a standard array. Indexes of a
# ring "wrap around" so that numbers higher
# (or lower) than the boundaries of the ring
# access the next position.

# Example 2: Ring

comment do
  scale_ring = (ring :C4, :D4, :E4, :F4, :G4,
                    :A4, :B4, :C5)
  index = 0
  24.times do
  note = scale_ring[index]
  play note
  sleep 1
  index += 1
  end
end

# Exercise B
#   1) Change the index increment in Example 2
#      to index += 2. What happens?
#   2) Change the index increment in Example 2
#      to decrement:  index -= 1. What happens?