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   "source": [
    "> This is one of the 100 recipes of the [IPython Cookbook](http://ipython-books.github.io/), the definitive guide to high-performance scientific computing and data science in Python.\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# 11.7. Creating a sound synthesizer in the notebook"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "1. We import NumPy, matplotlib, and various IPython packages and objects."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
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   "source": [
    "import numpy as np\n",
    "import matplotlib.pyplot as plt\n",
    "from IPython.display import Audio, display, clear_output\n",
    "from IPython.html import widgets\n",
    "from functools import partial\n",
    "import matplotlib as mpl\n",
    "%matplotlib inline\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "2. We define the sampling rate and the duration of the notes."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "rate = 16000.\n",
    "duration = .5\n",
    "t = np.linspace(0., duration, rate * duration)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "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."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "def synth(f):\n",
    "    x = np.sin(f * 2. * np.pi * t)\n",
    "    display(Audio(x, rate=rate, autoplay=True))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "4. Here is the fundamental 440 Hz note."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "synth(440)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "5. Now, we generate the note frequencies of our piano. The chromatic scale is obtained by a geometric progression with common ratio $2^{1/12}$."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "keys = 'C,C#,D,D#,E,F,F#,G,G#,A,A#,B,C'.split(',')\n",
    "notes = zip(keys, 440. * 2 ** (np.arange(3, 3 + len(keys)) / 12.))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "6. Finally, we create the piano with the notebook widgets. Each note is a button, and all buttons are contained in an horizontal box container. Clicking on one note plays a sound at the corresponding frequency."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "container = widgets.ContainerWidget()\n",
    "buttons = []\n",
    "for note, f in notes:\n",
    "    button = widgets.ButtonWidget(description=note)\n",
    "    def on_button_clicked(f, b):\n",
    "        clear_output()\n",
    "        synth(f)\n",
    "    button.on_click(partial(on_button_clicked, f))\n",
    "    button.set_css({'width': '30px', \n",
    "                    'height': '60px',\n",
    "                    'padding': '0',\n",
    "                    'color': ('black', 'white')['#' in note],\n",
    "                    'background': ('white', 'black')['#' in note],\n",
    "                    'border': '1px solid black',\n",
    "                    'float': 'left'})\n",
    "    buttons.append(button)\n",
    "container.children = buttons\n",
    "display(container)\n",
    "container.remove_class('vbox')\n",
    "container.add_class('hbox')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "> You'll find all the explanations, figures, references, and much more in the book (to be released later this summer).\n",
    "\n",
    "> [IPython Cookbook](http://ipython-books.github.io/), by [Cyrille Rossant](http://cyrille.rossant.net), Packt Publishing, 2014 (500 pages)."
   ]
  }
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