<http://schema.org/description>
"If you\u2019re wanting to use the Web Audio API to make a synthesizer, there are four main types of sound wave you\u2019ll need to be familiar with first. These are sine, square, triangle and sawtooth. A sine wave..."^^<http://www.w3.org/2001/XMLSchema#string>
<https://blog.stuartmemo.com/making-sine-square-sawtooth-and-triangle-waves/>