+ "Our ears interpret a changing pattern in air pressure as sound. If the pressure pattern repeats periodically, we experience a sensation of **pitch**.\n",
+ "\n",
+ "Pitch is determined by the pattern's **frequency** (i.e. the number of times per second that the pattern repeats). The actual *shape* of the pattern only affects what we call the _timbre_ of the sound (note: _affects_ not _determine_; many more things go into our sense of timbre). "
+ "The actual mechanics of sound production will enter the story a bit later. For now, let's use the simplest form of periodic patterns, namely, **sinusoids**. "
+ "It was known since antiquity that two vibrating strings sound well together if the length of the second string is **two thirds** of the first. This correspond of a frequency scaling factor equal to $3/2 = 1.5$\n",
+ "\n",
+ "The $3/2$ frequency ratio is called a **fifth** (for anachronistic reasons that will be clear later...)"