7. Music pitch

See: https://microbit-micropython.readthedocs.io/en/stable/music.html

7.1. Sound effects using pitch

music.pitch(frequency, duration=-1, pin=pin0, wait=True)

Plays a pitch at the integer frequency given for the duration specified in milliseconds.

Only one pitch can be played on one pin at any one time.

If duration is negative the pitch is played continuously until either the blocking call is interrupted or, in the case of a background call, a new frequency is set or stop is called.

An optional argument to specify the output pin can be used to override the default of pin0. pin=None causes no sound to play.

If wait is set to True, this function is blocking.

The code below increases the pitch in steps of 16 with playing duration of 20 ms.

from microbit import *
import music

for freq in range(880, 1760, 16):
    music.pitch(freq, duration=20)

The code below alters the pitch as the microbit is tilted sideways.

abs(accelerometer.get_x()) * 4 uses the absolute function to turn negative values into positive. Multiplying by 4 increases the maximum pitch that can be produced.

A-button pressing is required to make the sound.

from microbit import *
import music

while True:
    if button_a.is_pressed():
        music.pitch(abs(accelerometer.get_x()) * 4, 25)

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Tasks

1. Modify the code to increase the pitch in steps of 32 with a duration of 40.

2. Modify the code to decrease the pitch instead.

3. Modify the code to increase then decrease the pitch.

4. Modify the accelerometer code example to include B-button pressing for a duration of 100ms.

Q1

Modify the code to increase the pitch in steps of 32 with a duration of 40.

from microbit import *
import music

for freq in range(880, 1760, 32):
    music.pitch(freq, duration=40)

Q2

Modify the code to decrease the pitch instead.

from microbit import *
import music

for freq in range(1760, 880, -16):
    music.pitch(freq, duration=20)

Q3

Modify the code to increase then decrease the pitch.

from microbit import *
import music

for freq in range(880, 1760, 16):
    music.pitch(freq, duration=20)
for freq in range(1760, 880, -16):
    music.pitch(freq, duration=20)

Q4

Modify the accelerometer code example to include B-button pressing for a duration of 100ms.

from microbit import *
import music

while True:
    if button_a.is_pressed():
        music.pitch(abs(accelerometer.get_x()) * 4, 25)
    elif button_b.is_pressed():
        music.pitch(abs(accelerometer.get_x()) * 4, 100)

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7.2. Note frequencies

The table below has the frequencies for notes from A to A over 2 octaves.

The frequency of any note is doubled when going up one octave.

Note	Frequency
A4	440
B flat	466
B	494
C	523
C sharp	554
D	587
D sharp	622
E	659
F	698
F sharp	740
G	784
A5 flat	831
A	880
B flat	932
B	988
C	1046
C sharp	1108
D	1174
D sharp	1244
E	1318
F	1396
F sharp	1480
G	1568
A6 flat	1662
A	1760

---

The code uses a for-loop to play each frequency.

the A-button can be pressed to exit the while-loop using break.

Pressing the reset button on the back of the microbit will restart the code.

from microbit import *
import music

Am_4 = [440, 494, 523, 587, 659, 698, 784, 880]
timing = 400
while True:
    for freq in Am_4:
        music.pitch(freq, duration=timing)
    if button_a.was_pressed():
        break

---

Tasks

1. Modify the code to play the pitches of the E minor scale. See: https://www.piano-keyboard-guide.com/e-minor-scale.html.

2. Modify the code to play the pitches of the D major scale. See: http://www.piano-keyboard-guide.com/d-major-scale.html.

Q1

Modify the code to play the pitches of the E minor scale. See: https://www.piano-keyboard-guide.com/e-minor-scale.html.

from microbit import *
import music

Em_freqs = [659, 740, 784, 880, 988, 1046, 1174, 1318]
timing = 400
while True:
    for freq in Em_freqs:
        music.pitch(freq, duration=timing)
    if button_a.was_pressed():
            break

Q2

Modify the code to play the pitches of the D major scale. See: http://www.piano-keyboard-guide.com/d-major-scale.html.

from microbit import *
import music

DM_freqs = [440, 494, 523, 587, 659, 698, 784, 880]
timing = 400
while True:
    for freq in DM_freqs:
        music.pitch(freq, duration=timing)
    if button_a.was_pressed():
        break

Tasks

1. Begin with the scale Am_4 = [440, 494, 523, 587, 659, 698, 784, 880]. Use list comprehension to create a new list, Am_5, in which the frequencies are multiplied by 2, but include the condition that the frequency is not 440. Scroll the octave number, without blocking the sound, when the octave list sounds start. See: https://pc-python.readthedocs.io/en/latest/python_advanced/list_comprehensions.html

2. Begin with the scale Am_4= [440, 494, 523, 587, 659, 698, 784, 880]. Use list comprehension to create a new list, Am_5, excluding 440 and a new list, Am_3, in which the frequencies are divided by 2, excluding 880. Scroll the octave number, without blocking the sound, when the octave list sounds start.

3. Begin with the scale Am_4= [440, 494, 523, 587, 659, 698, 784, 880]. Use list comprehension to create a new list, Am_54_rev, which is the reverse of Am_4, excluding 880. Show an up arrow when Am_4 is played and a down arrow for Am_54_rev.

Q1

Begin with the scale Am_4 = [440, 494, 523, 587, 659, 698, 784, 880]. Use list comprehension to create a new list, Am_5, in which the frequencies are multiplied by 2, but include the condition that the frequency is not 440. Scroll the octave number, without blocking the sound, when the octave list sounds start.

from microbit import *
import music

Am_4 = [440, 494, 523, 587, 659, 698, 784, 880]
Am_5 = [freq * 2 for freq in Am_4 if freq != 440]
print(Am_5)

timing = 400
while True:
    display.scroll(4, wait=False)
    for freq in Am_4:
        music.pitch(freq, duration=timing)
    display.scroll(5, wait=False)
    for freq in Am_5:
        music.pitch(freq, duration=timing)
    if button_a.was_pressed():
        break

Q2

Begin with the scale Am_4= [440, 494, 523, 587, 659, 698, 784, 880]. Use list comprehension to create a new list, Am_5, excluding 440 and a new list, Am_3, in which the frequencies are divided by 2, excluding 880. Scroll the octave number, without blocking the sound, when the octave list sounds start.

from microbit import *
import music


Am_4 = [440, 494, 523, 587, 659, 698, 784, 880]
Am_5 = [freq * 2 for freq in Am_4 if freq != 440]
Am_3 = [freq // 2 for freq in Am_4 if freq != 880]

timing = 400
while True:
    display.scroll(3, wait=False)
    for freq in Am_3:
        music.pitch(freq, duration=timing)
    display.scroll(4, wait=False)
    for freq in Am_4:
        music.pitch(freq, duration=timing)
    display.scroll(5, wait=False)
    for freq in Am_5:
        music.pitch(freq, duration=timing)
    if button_a.was_pressed():
        break

Q3

Begin with the scale Am_4= [440, 494, 523, 587, 659, 698, 784, 880]. Use list comprehension to create a new list, Am_54_rev, which is the reverse of Am_4, excluding 880. Show an up arrow when Am_4 is played and a down arrow for Am_54_rev.

from microbit import *
import music

Am_4 = [440, 494, 523, 587, 659, 698, 784, 880]
Am_4_rev = [freq for freq in Am_4[::-1] if freq != 880]

timing = 400
while True:
    display.show(Image.ARROW_N, wait=False)
    for freq in Am_4:
        music.pitch(freq, duration=timing)
    display.show(Image.ARROW_S, wait=False)
    for freq in Am_4_rev:
        music.pitch(freq, duration=timing)
    if button_a.was_pressed():
        break

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7.3. Accelerometer based pitches

The code below uses the accelerometer to choose the pitch and the note duration.

The scale function is used to scale the tilting range to the length of the notes list and the length of the durations list.

The pitches used are based on the E minor scale.

from microbit import *
import music

accelerometer.set_range(1)

# A selection of E minor notes
notes = [164.81, 185.00, 196.00, 220.00, 246.94,  # E3, F#3, G3, A3, B3
        329.63, 369.99, 392.00, 440.00, 493.88,  # E4, F#4, G4, A4, B4
        659.25, 739.99, 783.99, 880.00, 987.77,  # E5, F#5, G5, A5, B5
        1318.51, 1479.98, 1567.98, 1760.00, 1975.53]  # E6, F#6, G6, A6, B6

# note lengths 4 ticks per beat or per 500ms
durations = [125, 250, 500, 1000, 2000]

durationlen = len(durations)
notelen = len(notes)

play_music = True
while True:
    #use A to toggle music
    if button_a.was_pressed():
        play_music = not play_music
    if not play_music:
        continue
    #get accelerometer readings
    x_reading = abs(accelerometer.get_x())
    y_reading = abs(accelerometer.get_y())
    # use above 1023 incase some microbits give slightly higher readings
    scaled_x = scale(x_reading, from_=(-1200, 1200), to=(-notelen +1, notelen -1))
    scaled_y = scale(y_reading, from_=(-1200, 1200), to=(-durationlen +1, durationlen -1))
    #get a note based on tilt
    pitch = notes[scaled_x]
    duration = durations[scaled_y]
    music.pitch(int(pitch), duration)

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Exercise

1. Use the accelerometer to control 8 pitches of a scale over just one octave.