Howdy,
I first heard about riff-writing from book editor Elizabeth Lyon when she visited my writing group a few years back. The riff in riff-writing is taken from jazz as in be improvisational. When I initially heard about the technique, I was skeptical. I'm not into jazz.
Recently, I started reading Manuscript Makeover written by Ms. Lyon. I must admit it's a pretty handy book, chock-full of good advice. In the opening chapter, she discusses how to add style to a manuscript. One of the techniques she encourages is…wait for it… riff-writing. I'm no longer skeptical about this technique. I think it works really well during editing/rewriting. Have a spot in your manuscript that is too tight, too terse, lacks characterization? Riff-write! Basically, by allowing yourself to be improvisational, you can open up the scene or dive deeper into characterization. Hopefully, by doing so, you'll add that enigmatic panache– style – to your writing.