Product Description and Specs Schematics and Manuals
Articles Regarding Beigel Sound Lab Links
For Mike Beigel's Current Products Go To Mu-FX.com

Mike Beigel founded Mu-FX in 2013 in Encinitas, California. Mu-FX is dedicated to the modern all-analog refinement and re-issue of the classic Musitronics product line including the; Mu-Tron III, Octave Divider, Phaser, Bi-Phase and others.

The first Mu-FX product was introduced in 2013. Based on the original Mu-Tron III, the first and best envelope filter pedal ever, the newly developed Tru-Tron 3X retains all the "mojo" that made the original pedal so popular.


BSL Envelope Controlled Filter
Historical Profile (no longer produced)

elliott randallBeigel Sound Lab was formed in 1971 and provided product prototypes of musical products. The first prototypes of a unique synthesizer and "Timbre Generation" filter bank were produced for Guild musical instruments by Mike Beigel and Isidor Straus. Then Mike Beigel set up Beigel Sound Lab to finish the production engineering and final prototypes. Shortly afterwards, Guild's president Al Dronge was killed in an airplane crash and Guild dropped the synthesizer project. We then produced a prototype envelope controlled filter from some components of the original Guild synthesizer, then formed Musitronics Corp and invented the Mu-Tron III and other products. In 1978 Musitronics was sold to ARP instruments and I re-started Beigel Sound Lab to provide musical product design services on a consulting basis.

A prominant musician had asked for a more sophisticated version of the Mu-Tron III, so I designed the rackmount Beigel Sound Lab Envelope Controlled Filter and had about 50 manufactured in 1980. Many prominant musicians including Elliott Randall, Marlo Henderson, Tim Bogert, Michael Iceberg, Jeff Baxtor, and Will Lee used them.

In 1996 I started working with Mike Matthews of Electro Harmonix and have devoted all my musical product work to Electro-Harmonix since then leading to the development of the Q-Tron. However, we still service Beigel Sound Lab and Mu-Tron vintage equipment, and have a few selected units for sale from our in-house collection.

Mike Beigel

In 2004 EHX released the highly anticipated studio quality Bi-Filter with roots deeply connected to that of the 1979 BSL Envelope Controlled Filter.

1979 BSL Envelope Controlled Filter

2004 EHX Bi-Filter

If you want the original sound and circuitry of the Mu-Tron III, please buy either a used vintage original Mu-Tron III (and NOT the so-called "Mu-Tron III plus" which is not a vintage original Mu-Tron III ).

Better yet, get my new MU-FX TRU-TRON 3X which has new features and better specs and retains all of the Mu-Tron III mojo.


Electro Harmonix, where history, quality and innovation collide. Electro Harmonix features the latest productions of the Mu-Tron legacy, the Q-Tron. For more than 30 years, they've been inspiring musicians with groundbreaking effect pedals, vacuum tubes and accessories.


Looking for the modern equivalent to the Mu-Tron?
A brief Mu-Tron history lesson..

Mu-Tron III

The Mu-Tron III by Musitronics Corp. first came out in 1972. Since 1996 the Q-Tron developed by Electro Harmonix had been the successor to the legacy which is the Mu-Tron. In early 1995 Mike Beigel was commissioned by Mike Mathews (owner of EHX) to reinvent the sound of Mu-Tron, today EHX still sells that sound as the Q-Tron.

1996 EHX Q-Tron
1998 EHX Q-Tron+
2000 EHX Mini Q-Tron
EHX has released several other units with roots tied to Mu-Tron. In 1998 the Q-Tron+ was released with technologies similar to the BSL below. In 2000 a Mini Q-Tron was developed similar to that of the original Mu-Tron.
Click on the pictures below to see ads and reviews for the Q-Tron: "The Envelope, Please," reprinted from the March 1998 issue of Guitar World and "Get Down, Get Funky," reprinted from the January 1998 issue of Guitar Shop.

(click each to enlarge)

Be sure to click the EHX products above to visit their homepage. Sound clips are available featuring the products and your favorite artists!
©2001-2014 Mike Beigel. All rights reserved.