One thing not meantioned for bluegrass is the limitation of instruments in the genre. Stringed instruments only and acoustic, sometimes amplified with a microphone. Further, the banjo is only 5 string, not 4 string tenor or plectrum. The mandolin often takes a percussion role through the use of "Chop Chords". Other allowed instruments are: fiddle, stand up bass, guitar.
Often instrumental breaks are playedwith fiddle, mandolin,banjo and sometimes guitar taking turns.
Another noteworthy and unknown to some item is that Bill Monroe's first banjo player was Dave Akeman, known as Stringbean, the country comic from the TV show Hee-Haw. Stringbean and his wifw Estelle, were murdered about 1975 by 2 men who were waiting in their home when they came home from his last performance at the grand old Opry. Their bodies were found by Grampa Jones, who lived across the road.
just for interest.