What is this flat thing on Ray Chen's bridge?

Question

A recently released video of Ray Chen playing Clair de Lune shows what appears to be a strange flat object on the violin bridge.

I thought originally that it was maybe part of the tailpiece or chinrest, however when he moves around, it does look like it's part of the bridge.

My thoughts are:

• Some form of microphone? (Microphones typically go near, or under the bridge, unless this is a type I am unfamiliar with)
• A strange mute? (Normally a concert mute is a small round rubber object that is on the middle two strings, and why would he use a mute for a piano duet?)

Here is a screenshot of the video:

Answer 1

It's actually an American one-dollar bill bill, folded and rolled up which he uses as a mute. Asked him post-concert after the recital the screenshot is from. He also revealed this in a post on his Instagram.

Answer 2

I'm pretty sure it's a mute. Violin mutes come in various forms as well as the 'quick access' type favoured by orchestral players. This is the classic type (though not the type we see in the video).

You can play a violin (or a brass instrument) very quietly without a mute. Or quite loud with one. The mute is about getting a DIFFERENT sound, not primarily a quieter one. The recording sounds like he's using a mute.