Alchemy is software for sketching or drawing using a computer. Unlike other paint programs, Alchemy is not necessarily about creating finished artwork, instead it focuses on using experimental interaction to come up with new ideas completely. 'Experimental interaction' in this case means things like using your voice to control how lines are drawn on screen, generating random shapes, or drawing with symmetry to create a quick and dirty face or body.
You might use Alchemy to draw for fun and experiment with, or if you're a more serious artist you might use it as a digital sketchbook - a place where you can experiment with new forms and drawing techniques. For example, like in the image below, you can create a quick and chaotic silhouette in Alchemy then later move to a more conventional paint program to add the finishing touches.
First time users may notice that Alchemy is missing a lot of the features we expect paint programs to have: no undo, no selecting, and no editing! But don't worry, this is all part of the plan to output a great number of good, bad, strange, and beautiful shapes, rather than a single 'perfected' one. To keep track of all these sketches we will make, Alchemy has a recording function that saves pages in a PDF (Portable Document Format) file either manually or automatically.
You can install and run Alchemy on Mac OS X, Linux, and Windows. Drawing can be done with a mouse or laptop touchpad, but a pen tablet is the best choice.