To recap the relevant points of these posts:
Drops from: Skeletal Guardian (only thing i've seen and heard of them dropping from, regardless of what it says up top)
Level for effect: Lvl 1 (again, disregard the info above). It's the only piece of Singing Steel armor that is not a clicky effect, nor is it a proc, it is a worn effect. Any level bard can equip this and breathe easy ... or not need to breathe rather.
Price: I've seen it for as low as 1100pp on Tholuxe Pealls, but usually 2k or more.
I just lost the roll on these while in a group camping the entrance area, only pulling from as far away as the left and right courtyards. My bard friend will be very sad since I would have given them to him rather than sell them.