03 Cooper with 63K -- runs great... except

I hear a noise at around 3000rpm when I shift through gears 1,2 & 3. The noise is not present in gears 4 & 5, as well as below 3000rpm, and when the A/C is off. The noise is a mid-range frequency, somewhat like a whine, and changes pitch when the clutch is engaged. (i.e. the whining pitch gets lower and goes away as the rpm decrease when clutch is engaged.) The noise is audible, but is not so loud that it draws immediate concerns.

The A/C works exceptionally well. The clutch and transmission are new.

any ideas? Thanks!!