This experiment emerged from my efforts to synthesize wave forms "by hand." As I was studying
the wave forms of various sounds, I thought it would be fun to draw those wave forms and use those drawings as a means to generate the corresponding audio.
This experiment is "incomplete" because, when I started, I didn't appreciate the fact that even relatively simple sounds have extremely complex, detailed wave forms and, without a ton of patience and a lot of computational power, it is not possible to sketch those.
Nonetheless, this demo is fun to play with. Use your mouse to sketch a wave form on the canvas. Make it as smooth or as jagged as you wish. Then hit the "start" button. The program will translate the coordinates of your sketch into a wave form for which the y-coordinates correspond to amplitude values. You can modulate the resulting sound using the Volume, Filter, and Rate controls, essentially making this a free-hand synthesizer rather than a oscillator-driven one. (You can also instruct the page to modulate the filter levels itself using the 'Auto Filter On' button. This creates a nice sweeping effect for many wave forms. The 'R2-D2' button randomly samples playrate values.)
The drawing you create will not be reproduced as a sound wave exactly, partly because I've taken a few processing shortcuts. For example, the x-axis provides a convenient way to think about time while drawing, but, in fact, it does not represent time explictly. Instead, as you're drawing (in real time), the y-coordinate of the mouse is pushed into an array. As a result, where (with respect to the x-axis) you draw is irrelevant to the wave being built. Fortunately, the removal of this constraint gives you more freedom to explore. Try writing your name. Or drawing a cat. Or creating vertical or diagonal streaks. Try drawing a circle (the easiest way to make a sine wave). There are a lot of neat things that can be created.
If your computer can handle it, one way to create some rich sounds is by opening this page in 4 or more tabs and having multiple waves playing at once, each of which being auto-filter modulated. Here is a brief sample of ambient drones from an experiment involving 6 tabs rendering distinct waves at once.
When you press "start", the program will show you, in a dark-blue color, the curve it has imputed from your drawing and that is being rendered as audio. The program will automatically loop the wave and continue to play it until you press "stop." If you ignore the x-axis and simply draw, draw, draw, you can make a longer audio clip. But these longer curves take longer to process and may slow your machine. A typical curve, drawn from the left to the right, will produce a sound wave about a tenth of a second long before looping back on itself.
The page opens with a pre-drawn sine wave--a form considered a pure tone. In digital audio, this is a primitive that can be duplicated and manipulated to re-create any sound. You can hear this pure tone as a starting point by pressing "start." In my opinion, this particular wave form, combined with moderate reverb and the R2-D2 function, produces some really nice sounds.