Spontaneous Combustion was an American music group founded in 1986. They performed what they called “bluerock”, a bluegrass/rock musicfusion. The band consisted of Roger Eilts (guitar, vocals), Leo Eilts (bass, vocals), Scott Prowell (mandolin, banjo, dobro, vocals) and Marvin Gruenbaum (violin, vocals). They often were billed as The Spontaneous Combustion Bluegrass Band or when they performed with former members of Total Strangers as Spontaneous Combustion/Total Strangers. They were a popular act at the Sante Fe Trails Bluegrass Festival and the Walnut Valley Festival.
Cirith Ungol has played covers of Spontaneous Combustion. Unfortunately I have no info about which, when and where.