Electro-Harmonix NANO Q-TRON Envelope Controlled Filter PedalEnvelope controlled filter is an effect type that ventures beyond the mainstream yet is equally at home in a wide range of genres and equally effective on guitar, bass, keys, horns and more. Electro Harmonix is a pioneer in this effect category and has been making envelope controlled filter pedals since the 1970s! The Nano Q Tron springboards off that deep heritage. Heres how it works: The Nano Q Tron responds to the users playing style and dynamics.