Envelope follower that produces a variety of sounds. - Brand: electro-harmonix - Model Name: micro QTRON - Type: Envelope Follower - Controls: MODE, Q, DRIVE - Bottom: Velcro attached - Box and other accessories included Used a few times at home, so there are some minor scratches and dirt. Please refrain from purchasing if you are concerned. Operation has been confirmed. (The following is the manufacturer's description) The small Q-Tron. An envelope-controlled filter that responds accurately and quickly to the strength of your picking. The cutoff frequency changes according to the size of the input signal, and the pitch of the filter changes at the same time. In addition to the three modes of HP/BP/LP, Q is also adjustable, achieving a variety of sounds despite its compact size. Type: Electric Guitar Type: Electric Guitar