Having gained his doctorate in 1929, Carpenter was awarded a Sheldon Fellowship from Harvard to continue collecting folksongs in Britain. He bought a car and began to travel England, Scotland and Wales in search of singers. Among the people he encountered were some who had sung for the Edwardian folksong collectors, such as Cecil Sharp and Gavin Greig, and some who would be visited by later collectors, such as Hamish Henderson and Kenneth Goldstein. He also located prolific singers never recorded before or since, such as Bell Duncan, an 80-year-old woman from Aberdeenshire, Scotland, whom he described as 'the greatest ballad singer of all time'. Her repertoire, according to Carpenter, consisted of some 300 songs, including 65 of the classic ('Child') ballads.
Carpenter's collecting method for songs was in many cases to record several stanzas of a singer's rendition using the Dictaphone cylinder machine. He then asked the singer to start again and dictate the words of the song, two lines at a time, while he typed them up on a portable typewriter.
By 1933, Carpenter had broadened the scope of his collecting to include mummers' plays as well as traditional songs. A few of these are recorded on cylinder, but many were apparently dictated to Carpenter, mostly by ex-performers.
Carpenter returned to Harvard in 1935 where he gave occasional lectures and set about transcribing the tunes of the ballads he had collected, a task in which he was self-taught. His aim was to publish the ballad material. He continued to work on the ballads in his collection following a move in 1938 to Duke University, where he took up a part-time position in the English Department, then chaired by the eminent North Carolina folklorist Frank C. Brown. The publication never materialised, however, and only a handful of items from his collection were ever published, despite his plans. During his time at Duke, Carpenter also continued to collect and encouraged his students to do so too.
Carpenter left Duke in 1943 and took up further posts in Virginia and finally as Head of the English Department at Greensboro College, North Carolina, where he stayed until his retirement in 1954. He returned to Booneville in 1964 where he began writing popular songs. In 1972, he sold his collection to the Library of Congress. He died in 1983.
For more information on Carpenter, see Julia C. Bishop, '"Dr Carpenter from the Harvard College in America": An Introduction to the James Madison Carpenter and his Folklore Collection', Folk Music Journal 7.4 (1998): 402-20.