I just put the bike on the workstand, and was honestly amazed to hear (what I think is the sound) coming from the rear derailleur pulley area. I'm not 100% convinced yet, but it looks like I've been duped! I was sure the sound was coming from the front of the drivetrain. I even stopped on the bike several times, but never heard the sound from the rear drivetrain area. I know sound can travel through the frame, and be difficult to diagnose on the road, but this is ridiculous. Sometimes I think I'm going insane when wrenching my bikes. (shaking head)