The autoharp as we know it today was invented by Charles Zimmerman in the 1870s, and is not a harp at all, but a chorded zither. ("Autoharp," like Band-Aid and Kleenex, is actually a trademark.) Zimmerman hoped to use the instrument to establish his own system of music notation. The notation was not a success, but the instrument was, becoming hugely popular in the Gay 90s. In the first few decades of the 20th century it was introduced to rural Southerners via mail-order catalogs and traveling teacher-salesmen. The primary attractions of the autoharp to rural musicians were its novelty, initial ease of playing, and its playing of chords, a novelty to musicians used to the melody of fiddle and voice or the melody and drones of the banjo. The most important group in the early history of commercial country music, The Carter Family, mixed the new sound of the autoharp with the equally-new guitar. Less attractive was lack of expression due to fixed strings, the instrument's quietness, seated playing position, and need for frequent, skilled tuning. (Pop Stoneman: "People were lost when they went out of tune. I bet there are thousands of 'em up in garrets for that reason.")
Ernest "Pop" Stoneman was the first to record with the autoharp, using the instrument solely as accompaniment. The most important musician to play lead on the 'harp was Maybelle Carter, the guitarist and harmony vocalist for the original Carter Family, who took a few clearly melodic breaks on the early 50s recordings with her daughters, "Fair and Tender Ladies" and "I Never Will Marry." Maybelle also evolved the style of playing the autoharp held vertically against her chest so she could stand and work a microphone, a style used by practically everyone today. (Autoharps are designed accordingly, with the chord bars positioned toward the wide end of the 'harp.)
If you're interested in the autoharp, a good place to start is the Smithsonian Folkways reissue Masters of Old-time Country Autoharp. This contains music originally released in the 60s by the Folkways record company, featuring Pop Stoneman, Kilby Snow, and Neriah and Kenneth Benfield, and has excellent, extensive notes.
