Here's an interesting bit on the Bose QC2s (not the original QC1s.)

AA had them "enhanced" for AA service - gray packaging and AA logos on the headphones, presumably making it more challenging to remove them from the aircraft (as in "steal them".) The also decided to prevent cord loss by permanently fastening the audio connect cord to the headset. Unfortunately, the QC2 has the volume control on the plug that goes into the headphone cup - and AA had the two-position switch fixed in the HIGH volume position.

This means that if you like to sleep, etc., with low background music / audio on, you are out of luck, because if you attempt to turn the seat control volume down to background listening levels, the audio will cut off entirely.

The answer is simple, small and cheap , unlike most tech solutions today . Get a Radio Shack Model 42-2559 Gold-Plated Volume Control Cable for Stereo Headphones (technically, an in-line variable attenuator with 12" / 30 cm of cable) and insert it between the Bose audio cable connector and the seat audio plug. Cost? $6.59 plus tax - tiny, easy to travel with.

If I am going to be on an AA 763 or 777 with Bose QC2 service, this is one thing I never do leave home without. (I'd not go on about this again, but until "Search" returns...)