my 2004 silverado 5.3 is making a high pitched swell from the belt and pulley system . It sounds like it the ac compressor kicking on and off just with lots of noise ? tentioner or compressor ?

Locating a noise is one of the hardest things to find. You need to go step by step and try different things. First change tge belt and see wgat hapoens, if the noise is still there change the tension. Its not normal for a A/C compressor to turn on and off fast, you may be short your refrigerant charge.

Remove the belt aND spin each of the pullies ,alternator etc. Separately .most of the time on those it'll be both idler and tensioner pullies they aren't the best designed and are a regular issue also the alternators on those have a weak /cheap front and rear bearing that also makes a hug pitched screech /chirp .if you spin the the alternator freehand you can usually hear that same.noise . I have 4 GMCS I just change all 3 if alternator is making noise as a gonna hafta do it anyway kinda thing. They don't make things like they used to ..Good luck

Oh sorry as Joe Mon mentioned if your A/C is short cycling it is either low in freon or low side pressure switch is going bad . Bet on low freon .lol ..also of your high pitched squeal is excessively loud and hurts your ears take a.look at Ac clutch .if it's bad it can make.a.racket .yanno just before it just quits working all together .lol