Pat Conte's informative notes to Yazoo's CD reissue of Washington Phillips' 'I am born to preach the gospel' (Yazoo 2003)include a description of the dulceola and a reprint of an advert for the dulceola (complete with picture and described as 'A Miniature Grand Piano'). The advert appeared in the prestigious magazine 'The Etude' in 1907. The inventor was David P. Boyd who left his tyre business and family company to produce the doceola as an aid to beginning pianists. The following excerpt may be of interest:
'The dolceola was constructed of a zither-like body with 60 wire strings with a housing atop it similar to an autoharp holding, instead of bars, 25 chromatic notes on a miniature keyboard for the right hand. For the left hand, there was a setup for 7 chords played in cluster of three keys each giving the three notes of the chord, a tonic note or root and the fifth. Boyd based the tuning on Eb in an effort to give a comfortable range for accompaniment of both male and female voice. Its setup would also allow for easy progression in C minor to facilitate singing. Phillips had limited the breadth of his chordal possibilities by tending to remain a full step removed from Eb (as Boyd had engineered the system). Conversely, as he preferred F# for most of his accompaniments throughout his repertoire, the penatonic scale he predominantly set to his work affords him a marked virtuosity in the reliance of mainly black key for the right hand'.
Conte does not mention Paul Mason Howard by name, but simply says '... the dolceola was used on one other session in the 1940s by a white pianist accompanying Leadbelly (and even then erroneously described as a zither)'.