Strange Buzz and Vibration - 2500 - 3000 rpm

[over_the_hill]

As the thread title says.

I was out yesterday and developed a strange buzz / vibration - sounded like something metal was a bit loose but only between 2500 - 3000 rpm so likely a resonance of some sort.

It sounded like it was right behind the radio at the back of the engine bay.
If I dipped the clutch while in that rev range the noise stopped.

Otherwise the car was performing as normal.

Any thoughts or ideas on what to look at - another job for the weekend !!