While the vast majority of acoustic guitars have round soundholes, early Gibson archtop acoustics such as the L-5 and Super 400 substituted “f”-shaped soundholes in the 1920s and ’30s, which are patterned after the soundholes found on traditional bowed string instruments such as the violin, viola, and cello.
Eventually, Gibson added pickups to its archtop guitars, but kept the f-holes. By 1958, Gibson began building the ES-335, which had f-holes, as well as a solid block of maple running down the middle of the guitar to help eliminate feedback. Other manufacturers such as Guild and Gretsch followed Gibson’s lead and used traditional f-holes on their hollowbody guitars. Oddly enough, Gretsch eventually stopped employing f-holes in their hollowbodies and substituted painted-on decorative substitutes, most likely to help reduce feedback problems at high volume levels.