Creating a sound synthesizer in the Notebook

In this recipe, we will create a small electronic piano in the Notebook. We will synthesize sinusoidal sounds with NumPy instead of using recorded tones.

How to do it...

1. We import the modules:

   >>> import numpy as np
       import matplotlib.pyplot as plt
       from IPython.display import (
           Audio, display, clear_output)
       from ipywidgets import widgets
       from functools import partial
       %matplotlib inline

2. We define the sampling rate and the duration of the notes:

   >>> rate = 16000.
       duration = .25
       t = np.linspace(
           0., duration, int(rate * duration))

3. We create a function that generates and plays the sound of a note (sine function) at a given frequency, using NumPy and IPython's audio class:

   >>> def synth(f):
           x = np.sin(f * 2. * np.pi * t)
           display(Audio(x, rate=rate, autoplay=True))

4. Here is the fundamental 440 Hz note:

   >>> synth(440)

   
5. Now, we generate the note frequencies of our piano...