However, attempting to classify Rock and Roll as a single genre continues to be difficult as it can encompass a wide variety of musical forms. It can be as carefully crafted as a song by Queen, or an album produced by Phil Spector, or as straightforward as a three-chord composition by The Ramones, or as poetic as a song written by Bob Dylan. Although it is clearly defined by the use of guitars and drum kits, virtually no instrument can now be excluded from a rock band, including the piccolo trumpet used in The Beatles' Penny Lane, the cello that graced most of the work of the Electric Light Orchestra, or even "Weird Al" Yankovic's accordion. Rock revolutionized theater. See rock musical and rock opera.