High pitched Squeal while off the accelerator

Hi,
First time here and am trying to figure out what's going on with my taco. There's a high pitched squeal that happens when my truck is idling/everytime I take my foot off the accelerator. I thought it was my serpentine belt. I replaced that today with no improvement. The sound definitely seems to be coming from the driver's side under the hood but I can't quite identify what's up. Any help on what I should be looking at would be helpful. I have tried to upload a video to let you hear what I hear but .MP4 wasn't an accepted file type. If you know how what's going on and maybe how I can share that video with y'all I'd appreciate it.

 

You probably have something not spinning which should be spinning, and the belt is squealing as it slips over it. Could be a seized idler pully. Does your air conditioning work? Could be the compressor. Is your battery light illuminated on the gauge cluster? Could be the alternator. Idler pully would be my first guess though.