Jeffrey Thomas Thacher (born December 23, 1967) is an American musician, best known as a member of the vocal group Rockapella. A professional vocal percussionist and singer who emerged on the early contemporary a cappella scene in 1991, Jeff Thacher co-founded the Boston-based a cappella group Five O'Clock Shadow (aka FOCS) that year and went on to join Rockapella in 1993 as their full-time mouth-drummer.

Thacher was a 1990 graduate of Berklee College of Music's Music Production & Engineering program, and afterward spent several years in television & radio production when not performing^[1][2]

In 1991 Thacher performed as a tenor in Five O'Clock Shadow, when Rockapella was looking to add human-made drum sounds to their live shows.^[1][3] Thacher's first concert with the group was on May 15, 1993, at the Berklee Performance Center,^[1][4] after which he began touring internationally with Rockapella, making his first CD appearance with them on the song "Big Wet Rag" from the Carmen Sandiego soundtrack sequel Carmen Sandiego: Out Of This World (1993). The first album to feature Jeff's distinctive sound throughout was Rockapella's first all-originals album, Vocobeat (1994), for the Japanese market.^[5] Rockapella were still a quartet during their television stint on Carmen Sandiego until the fifth and final season of the show (1995) when Thacher appeared with them for that season.

As the mid-1990s progressed, the terms "organic" and "imitative" began to be used to describe contrasting a cappella vocal percussion styles, with Thacher as the most prominent progenitor of the "organic" approach, combining blatantly literal replication of drums with sounds that didn't seek to duplicate, but rather fill the role of a drum or percussive instrument.^[1][6][7] Thacher was also the first vocal percussionist to employ a throat microphone (aka "throat mic") using electronic guitar pickups adhered to the larynx area of the throat (see piezoelectric sensor). The technique allowed intentional throat grunting sounds to be heard more effectively in live shows and on recordings (1997).^[1] He became the first such artist to be professionally endorsed by a guitar pickup company (Seymour Duncan, from 1998 to present, now D-TAR).^[8]