from wiki... Instrumentation Unlike mainstream country music, bluegrass relies mostly on acoustic stringed instruments. The fiddle, five-string banjo, acoustic guitar, mandolin, and upright bass are often joined by the resonator guitar (popularly known by the Dobro brand name). This instrumentation originated in rural dance bands and was being abandoned by those groups (in favor of blues and jazz ensembles) when picked up by European-American musicians.[2] Instrumental solos are improvised, and are frequently technically demanding. The acoustic guitar is now most commonly played with a flatpick unlike the style of Lester Flatt who used a thumb and finger pick. The style is known as flatpicking. The banjo players often use a three-finger style developed by Earl Scruggs. Bluegrass musicians, fans, and scholars have long debated what instrumentation constitutes a bluegrass band. Since the term bluegrass came from Bill Monroe's band, the Blue Grass Boys, many consider the instruments used in his band the traditional bluegrass instruments. These were the mandolin (played by Monroe), the fiddle, guitar, banjo and upright bass. At times the musicians may perform gospel songs, singing four-part harmony and including no or sparse instrumentation (often with banjo players switching to lead guitar). Bluegrass bands have included instruments as diverse as the resonator guitar (Dobro), accordion, harmonica, piano, autoharp, drums, drum kit, electric guitar, and electric versions of all other common bluegrass instruments, though these are considered to be more progressive and are a departure from the traditional bluegrass style. These departures are sometimes referred to as "Newgrass".