1972 Series III - 88 - Gas Engine - ~80,000 miles

Can anyone help me diagnose the noise that I am hearing? It is a loud squealing noise that only happens when the vehicle is in gear and the clutch is let out. It almost sounds like a slipping belt. I never get the noise in neutral or when the clutch pedal is pushed down. I get the noise in all 4 forward gears. It shifts just fine. The noise is louder when accelerating. There is no change to driving performance. This is the second occasion that it has happened, and I bet the noise will be gone tomorrow morning. Here is a link to the noise.

https://youtube.com/shorts/ujZEjmvdRLQ?feature=share

I replaced the master and slave clutch cylinder in April and it has worked great since then.

I am guessing the clutch may be slipping, but would love an expert opinion.