The one source for this style of playing should be mentioned. From North Carolina, Obray Ramsay. 3 finger style banjo picking has bee around for a long time. Van Epps and other famous classical style banjo players employed the 3 finger technique in rags and "Characterisic" music.

The celtic aspects of bluegrass might emanate from the fiddle styles from Ireland and Scotland. They certainly were transferred to Eck Robertson, Clayton McMichen and Fiddlin' John Carson even though the styles were adapted to American blues patterns as well as Celtic.

The transfer to bluegrass came about when the early string band music became "listener" oriented rather than dance oriented. The Blue Sky Boys, the Delmore Brothers, the Baile Brothers as well as the Carter Family had a lot to do with it's development. Early Carter Family as well as others show the use of Hawaiian influences in the playing style of guitarists. It may be that the style that developed into dobro came from African-American blues musicians who developed the style of "teasing" the guitar strings with jackknives and broken whiskey bottle necks. There is a controversey as to whether this style was endemic to African-Ammerican blues musicians or came from Hawaiian sources.

I think the key to bluegrass is the fiddle because this is the instrument that induced breakneck speeds at the hoe-sowns and set-runnings in the mountains.

Frank