Here goes the most beautiful use of feedback noises:

Endless Nameless by Nirvana
This song is from the Nevermind album and it's played (sort off) when
they are smashing their guitars and drums on the end of shows

this song appears 15 minutes after the last song has ended.

Intro: Drop d for lower sound

E****
A****
D****
g
b
e

* means heavy palm muted repeat this over again with the CD
And then ad a verry heavy smash when play on the highest frets of your
guitar (as far as your hand gets into the cutaway)
 To ad a verry cool sound use full disstortion, keep tuning your high
 E string till it snaps and don't keep your guitar far from your amp
 This wil cause high sounds you usually don't want,but for playing
 Nirvana it's just part of the show