Originally Posted by DrumEatDrum
On the Van Halen album "Balance" there is one "song" that is nothing but Eddie Van Halen drunk, dropping things on the inside of his piano. Although I'm not really sure why they included that on an otherwise awesome album. hahaha
I expect for the usual reason - it seemed like fun at the time :)
Then there's Crimson's Thela Hun Ginjeet
where Bob Fripp covertly recorded Adrian B babbling nervously when he returned to the studio after a close call with muggers on the street.
One-off accidental elements of music are like photos of an unaware / unselfconscious subjects - often it will be nonsensical but when it's good the sincerity makes it great. Hence WC Field's famous line, "Never work with animals or children" ... apart from being messy and chaotic, they also tend to steal the show.