Just my $0.02
I had one squealing for a few minutes during a cold start up. It was the AC compressor serpentine belt. I replaced the belt because of the mileage I had on the rig. It still squealed. Rechecked the tension and so on, then one day it shredded under the hood. The bearing in the AC belt tensioner froze up. In hind sight the tensioner bearing was going bad and the tensioner pulley was giving resistance to the belt making it squeal. Now I run without AC never used it in the last 7 years so one of these days I have $30 for a tensioner and $12 for a belt burning a hole in my pocket and no other projects going on I'll fix it.
BTW this was on a VG33E 3.3L V6 2000 Nissan Frontier.