There are two ways that I have used. The cheap way is to buy a practice mute. Should be a couple of dollars at most. It's basically a weight with a clip that goes on the bridge, and you could probably easily make one yourself. There is a picture of a wooden mute on page
7 of the ILS catalog at
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It doesn't really show how the mute is applied, but the three fingers are slotted so that the mute sets on the bridge with the strings going through the gaps. They don't show a practice mute in the catalog, but you could get one of the wood mutes and either make a heavier copy, or mount a lead weight on it. The more weight in the mute, the quieter.
The other way is to use an electric practice instrument with headphones. I have a homemade 'stick' with a pickup that I paid a friend of mine about $100 to build for me. Commercial e-fiddles can cost several thousand dollars. You need a good pickup, a high-impedance preamp, and a headphone amplifier for this.
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