Python Audio Synthesis
 Python Audio Synthesis

Use
IPython.display
for Additive Synthesis in Python  Make Various Basic Wave Forms With Additive Synthesis in Python

Use
pyaudio
to Generate Audio Synthesis in Python
Today, we will learn about audio synthesis and how we can generate sound using Python.
Python Audio Synthesis
Sound synthesis or audio synthesis generates sound electronically (using hardware or software) that mimics the human voice or musical instruments.
Synthesis is primarily for music, where an electronic device/instrument known as a synthesizer is used to record and perform music.
Now, the point is can we use Python to generate these kinds of simple sounds, for instance, sine wave? Do we have any module for that, or how can we create our own?
Let’s learn the different ways below.
Use IPython.display
for Additive Synthesis in Python

First, we import the necessary modules and libraries. We import
IPython
to display sound player,numpy
for working with arrays,matplotlib
for plotting charts (we’ll be doing it while generating basic waveforms), andmath
to use mathematical functions.import IPython.display as ipd import numpy import math import matplotlib.pyplot as plt

Set the sample rate. Here, we set the
sample_rate
with22050
.sample_rate = 22050

Make the sine waveform.
def makesine(frequency, duration): t = numpy.linspace(0, duration, math.ceil(sample_rate*duration)) x = numpy.sin(2 * numpy.pi * frequency * t) return x
At this step, we define a function
makesine()
, which takesfrequency
andduration
as parameters. We useduration
innumpy.linspace()
andfrequency
innumpy.sin()
methods to reuse pure sine waveforms.Note that the
numpy.linspace()
creates numeric sequences, or we can say it returns evenly spaced numbers/samples w.r.t. interval (start,stop). It is similar to thenumpy.arange()
but takes a sample number (num
) as a parameter instead ofstep
.You can find more on that here.
On the other hand,
numpy.sin()
calculates the trigonometric sine for all the specifiedx
(an array of elements). 
Run
makesine()
.output = numpy.array(()) y = makesine(261.63, .5) # C for 0.5 seconds output = numpy.concatenate((output, y)) y = makesine(293.66, .5) # D for 0.5 seconds output = numpy.concatenate((output, y)) y = makesine(329.63, .5) # E for 0.5 seconds output = numpy.concatenate((output, y)) ipd.Audio(output, rate=sample_rate)
Next, we execute
makesine()
multiple times to form a new waveform with specifiedfrequency
andduration
. After that, we usenumpy.concatenate()
to place all of them together.You can find the complete working source code below with the respective output.

Here is the complete source code.
import IPython.display as ipd import matplotlib.pyplot as plt import numpy import math sample_rate = 22050 def makesine(frequency, duration): t = numpy.linspace(0, duration, math.ceil(sample_rate*duration)) x = numpy.sin(2 * numpy.pi * frequency * t) return x output = numpy.array(()) y = makesine(261.63, .5) # C for 0.5 seconds output = numpy.concatenate((output, y)) y = makesine(293.66, .5) # D for 0.5 seconds output = numpy.concatenate((output, y)) y = makesine(329.63, .5) # E for 0.5 seconds output = numpy.concatenate((output, y)) ipd.Audio(output, rate=sample_rate)
OUTPUT:
[python audio synthesis  ipython display.wav](/file/Python/python audio synthesis  ipython display.wav)
Make Various Basic Wave Forms With Additive Synthesis in Python
We are done with the basic sine waveform. Let’s experiment with various basic waveforms with frequencies at the integer multiples using frequency * i
; here, i
is the counter from 1
and increments by 1
every time.
We need to soften these sine waves into predefined amplitudes (amplist
), which are then stacked up in the output
. To make that happen, we are required to make a function named addsyn()
as follows:
def addsyn(frequency, duration, amplist):
i = 1
t = numpy.linspace(0, duration, math.ceil(sample_rate*duration))
output = numpy.zeros(t.size)
for amp in amplist:
x = numpy.multiply(makesine(frequency*i, duration), amp)
output = output + x
i+=1
if numpy.max(output)>abs(numpy.min(output)):
output = output / numpy.max(output)
else:
output = output / numpy.min(output)
return output
Inside the addsyn()
, we initialize a new output
. Inside the for
loop, we make the sine waveform with a maximum amplitude (amp
); here, frequency
is an integer multiple.
Then, we sum it to the output and save it in the output
variable. Next, we ensure that the maximum amplitude doesn’t exceed 1
and return the output
.
Now, we can execute the following piece of code to make only one harmonic sine wave and make a chart for it that shows only 0.005
seconds to see this waveform shape.
t = numpy.linspace(0, 1, sample_rate)
sinewave = addsyn(440, 1, [1])
plt.plot(t, sinewave)
plt.xlim(0, 0.005)
ipd.Audio(sinewave, rate=sample_rate)
The complete source code would be as follows.
Example Code:
import IPython.display as ipd
import matplotlib.pyplot as plt
import numpy
import math
sample_rate = 22050
def addsyn(frequency, duration, amplist):
i = 1
t = numpy.linspace(0, duration, math.ceil(sample_rate*duration))
output = numpy.zeros(t.size)
for amp in amplist:
x = numpy.multiply(makesine(frequency*i, duration), amp)
output = output + x
i+=1
if numpy.max(output)>abs(numpy.min(output)):
output = output / numpy.max(output)
else:
output = output / numpy.min(output)
return output
t = numpy.linspace(0, 1, sample_rate)
sinewave = addsyn(440, 1, [1])
plt.plot(t, sinewave)
plt.xlim(0, 0.005)
ipd.Audio(sinewave, rate=sample_rate)
OUTPUT:
[python audio synthesis  basic sine waveform harmonic.wav](/file/Python/python audio synthesis  basic sine waveform harmonic.wav)
Now, we can play around with different values of the addsyn()
function to get different outputs. See another example to create a square wave below.
Example Code:
import IPython.display as ipd
import matplotlib.pyplot as plt
import numpy
import math
sample_rate = 22050
def addsyn(frequency, duration, amplist):
i = 1
t = numpy.linspace(0, duration, math.ceil(sample_rate*duration))
output = numpy.zeros(t.size)
for amp in amplist:
x = numpy.multiply(makesine(frequency*i, duration), amp)
output = output + x
i+=1
if numpy.max(output)>abs(numpy.min(output)):
output = output / numpy.max(output)
else:
output = output / numpy.min(output)
return output
t = numpy.linspace(0, 1, sample_rate)
square_wave = addsyn(440, 1, [1, 0, 0.349, 0, 0.214, 0, 0.156, 0, 0.121, 0])
plt.plot(t, square_wave)
plt.xlim(0, 0.005)
ipd.Audio(square_wave, rate=sample_rate)
OUTPUT:
[python audio synthesis  basic sine waveform square.wav](/file/Python/python audio synthesis  basic sine waveform square.wav)
Use pyaudio
to Generate Audio Synthesis in Python
Here, we will use pyaudio
, a Python module recording audio with Python.

First, we import necessary libraries:
math
for performing mathematical functions andpyaudio
for generating waves.import math #import needed modules import pyaudio #sudo aptget install pythonpyaudio

Initialize
pyaudio
.PyAudio = pyaudio.PyAudio

Initialize variables.
bit_rate = 16000 frequency = 500 length = 1 bit_rate = max(bit_rate, frequency+100) number_of_frames = int(bit_rate * length) rest_frames = number_of_frames % bit_rate wave_data = ''
Here, we initialized the
bit_rate
with16000
, which shows the number of frames per second. Thefrequency
is set to500
Hz denoting the waves per second (261.63=C4note
) whilelength
is initialized with1
.After that, we use the
max()
function to find the maximum frombit_rate
andfrequency+100
and assign the maximum value tobit_rate
. Then, we multiply thebit_rate
andlength
, convert it toint
type using theint()
function and assign it tonumber_of_frames
.Next, we use the modulo operator (
%
) to dividenumber_of_frames
withbit_rate
and assign the remainder torest_frames
. Finally, we initializewave_data
with an empty string. 
Generate waves.
for x in range(number_of_frames): wave_data = wave_data+chr(int(math.sin(x/((bit_rate/frequency)/math.pi))*127+128)) for x in range(rest_frames): wave_data = wave_data+chr(128)
Here, we used two
for
loops that iterate until thenumber_of_frames
to generate waves. 
Record audio.
p = PyAudio() stream = p.open(format = p.get_format_from_width(1), channels = 1, rate = bit_rate, output = True) stream.write(wave_data) stream.stop_stream() stream.close() p.terminate()
Here, we created an instance of
PyAudio
, saved the reference inp
, and used that reference to open a stream using theopen()
method, which will record audio. Next, we wrotewave_data
, stopped the stream, and closed it. Finally, terminate thePyAudio
instance (p
) as well.You can read about
open()
,write()
,stop_stream()
, andclose()
here in detail. 
Here is the complete source code.
import math import pyaudio PyAudio = pyaudio.PyAudio bit_rate = 16000 frequency = 500 length = 1 bit_rate = max(bit_rate, frequency+100) number_of_frames = int(bit_rate * length) rest_frames = number_of_frames % bit_rate wave_data = '' for x in range(number_of_frames): wave_data = wave_data+chr(int(math.sin(x/((bit_rate/frequency)/math.pi))*127+128)) for x in range(rest_frames): wave_data = wave_data+chr(128) p = PyAudio() stream = p.open(format = p.get_format_from_width(1), channels = 1, rate = bit_rate, output = True) stream.write(wave_data) stream.stop_stream() stream.close() p.terminate()
Once we execute the above code, we can hear a wave. Note that we are not saving this wave in a
.wav
file.You may read here to learn about saving in a
.wav
file.