Activity: Making Music (Advanced)

31 Dec

Use the Rovers speaker to make it play songs. Learn to combine the world of music and robotics by going through sheet music and coding the Rover to play each note.

In the advanced code, we will make a system to allow us to write our entire song as a string and program the Rover to read the music by itself.

Basics of Music:

When it comes to reading sheet music for this task, we will be using two pieces of information from each note. The tone of the note and how long the note is played. The diagrams for music theory and the example song have been added underneath, but for further information on reading music, head over to ‘Activity: Making Music (Beginner)’.

Activity: Making Music (Beginner)

Code:

We will switch to the text code editor for the intermediate and advanced music activities as some of the following functions are easier to build in that editor. Unfortunately the block editor cannot be used for this code as we will be using python dictionaries which are incompatible with blocks.

Constant - A constant is a variable that never changes when the code is run. In python, we write this in all capitals with underscores between words.

Lists/Arrays - A list is an object that can contain many variables inside it. Lists can be looped through to access each of the elements. Head to ‘Activity: Making Music (Intermediate)’ to learn more about lists.

Activity: Making Music (Intermediate)

Dictionaries - A dictionary is an object that can access multiple variables like a list. The difference is that dictionaries have ‘keys’ assigned to each value instead of numbered indexes like a list. As seen below, dictionaries are written using curly brackets, with a key and value paired together using a colon. Both the key and value can be anything as long as all keys are unique.

Just like accessing list values, enter the key into the square brackets after the dictionary, and it will return the value assigned to that key. For further info on using dictionaries, we recommend visiting the guide to dictionaries by W3Schools:

W3Schools: Python Dictionaries

1) Setting the Constants:

As in the other ‘Making Music’ guides, we set the note lengths as constants. Next, we also set the octave as a constant (make sure the number is in a string).

We’re then going to organise our note lengths into our first dictionary. As seen in the code, create a ‘note_lengths’ constant dictionary. Here, we will assign a single letter to each constant. For example, we can use the key ‘C’ to get the length of a crotchet out. This makes coding faster as we only need to type a single letter for the note length.

CROTCHET = 0.5
MINUM = 2 * CROTCHET
SEMIBREVE = 4 * CROTCHET
OCTAVE = '4'

NOTE_LENGTHS = {
  'C': CROTCHET,
  'M': MINUM,
  'S': SEMIBREVE
}

2) Preparing Inputs and Outputs:

input_song = 'E/C D/C C/C D/C E/C E/C E/M D/C D/C D/M E/C G/C G/M'
output_song = []

We must write the input song in a format the following code can understand. Each note will be represented by the note tone and the note length letter combined by a forward slash. For example, a crotchet of E is E/C. Each note should then be separated with a space. An empty list will also be needed to store the output song.

We’ll print out the first two notes of the song string underneath at every step, so you can see how it changes:

Current Song = 'E/C D/C'

3) Break up the Input:

# Break up the string into each note
for note in input_song.split(' '):
  output_song.append(note.split('/'))

Next, we use the python ‘string.split(‘ ‘)’ to break the input song into a list. This breaks up the string at the spaces and puts the pieces into a list. Inside the loop, we do this again with the slashes to break each note into a list with tone and note length.

Current Song = [['E', 'C'], ['D', 'C']]

4) Attaching the Octave:

# Attach the octave to the tone
for note in output_song:
  note[0] += OCTAVE

We know that the Micromelon note system must take the tone and octave together, for example, NOTES.C4. Currently, each tone doesn’t have an octave attached to it. So we will loop through the ‘output_song’ and add the octave constant to each tone.

Current Song = [['E4', 'C'], ['D4', 'C']]

5) Translate to True Values:

# Translate the string to the true values
for note in output_song:
  note[0] = NOTES[note[0]]
  note[1] = NOTE_LENGTHS[note[1]]

The final step before we play the song is to convert the tone and the note length to their actual values. This is where the dictionaries come in. For the tone, we’re going to feed the tone into the ‘NOTES’ dictionary and feed the note length into the ‘NOTE_LENGTHS’ dictionary to get the actual values. Remember that notes are actually frequencies for the buzzer to play.

Current Song = [[329.63, 0.5], [293.66, 0.5]]

Play the Song:

# Play the song
for note in output_song:
  Sounds.playNote(note[0])
  delay(note[1])

Now, exactly like in the intermediate guide, we can loop through the ‘output_song’ and play the music.

Complete Code:

The complete code here will play the first line of the song. Try and fill in the rest of the song yourself! If you find your input song too long, try to make variables for each line and add them together to make your ‘input_song’.

CROTCHET = 0.5
MINUM = 2 * CROTCHET
SEMIBREVE = 4 * CROTCHET
OCTAVE = '4'

NOTE_LENGTHS = {
  'C': CROTCHET,
  'M': MINUM,
  'S': SEMIBREVE
}

input_song = 'E/C D/C C/C D/C E/C E/C E/M D/C D/C D/M E/C G/C G/M'
output_song = []

# Break up the string into each note
for note in input_song.split(' '):
  output_song.append(note.split('/'))
  
# Attach the octave to the tone
for note in output_song:
  note[0] += OCTAVE

# Translate the string to the true values
for note in output_song:
  note[0] = NOTES[note[0]]
  note[1] = NOTE_LENGTHS[note[1]]

# Play the song
for note in output_song:
  Sounds.playNote(note[0])
  delay(note[1])