The "chop" is a percussive string instrument technique pioneered by bluegrass fiddler Richard Greene in the 1960s and adopted into contemporary string styles by Darol Anger in the 1980s. This article traces the diffusion of the chop through a number of North Atlantic fiddling traditions in the 1990s and 2000s. It also considers the circumstances and implications of musicians' decisions to adopt, adapt, or reject the chop. Drawing on both sociological research on the diffusion of innovations and genre theory, this article demonstrates that the diffusion trajectory of a musical innovation depends on the innovation itself, on the sites of transmission, and on the interplay of the lived and imagined musical worlds within which musicians play, work, and study. It concludes by suggesting that, when studying North Atlantic fiddling, both regional divisions and generational trends should be taken into consideration. The violin is so old and the techniques are so well established. .. . And now all of a sudden there's a new thing, after how many years?-Casey Driessen (telephone interview, 1 February 2011) I n 1966, bluegrass fiddler Richard Greene invented a percussive string instrument technique that he dubbed "the chunky chop" (telephone interview, 1 February 2011). Now known simply as "the chop" or, in its verbal form, "chopping, " this technique is currently used by violinists, violists, and cellists in nu-Note: this article refers to figures and video clips that can be found on the Society for Ethnomusicology's website, following the pathway Publications > Journal > Multimedia Appendices. As of 2013, the URLs for the SEM website and the multimedia appendices are www.ethnomusicology.org and http://www .ethnomusicology.org/?Pub_JournalMA, respectively. merous musical genres, including traditional fiddling styles of the British Isles, Canada, Scandinavia, Spain, and the United States; jazz; progressive bluegrass, or newgrass; popular styles; and classical string pedagogy. In this paper, I trace the diffusion of the chop through a number of North Atlantic fiddling traditions. 1 I also consider the circumstances and implications of musicians' decisions to adopt, adapt, or reject the chop. Drawing on both sociological research on the diffusion of innovations and genre theory, I demonstrate that the diffusion trajectory of a musical innovation depends on the innovation itself, on the sites of transmission, and on the interplay of the lived and imagined musical worlds within which musicians play, work, and study. I conclude by suggesting that, when studying North Atlantic fiddling, we ought to consider not only standard geographic or regional divisions, but also generational trends. Like col legno (striking the strings with the wood of the bow) or sautillé (a rapid bouncing that uses the natural springiness of the bow), the chop is a technique specific to bowed string instruments. It consists of dropping the bow vertically onto the strings to make a crunchy, percussive noise, then picking it up off the strings with a slight h...