Monotron

Monotron (stylised as monotron in all lowercase) is the collective name of a series of miniature analogue synthesizers produced by Korg, a Japanese manufacturer of electronic musical instruments. There are three models in the series: the original Monotron, the Monotron Duo and the Monotron Delay.

Monotron

 

The original Monotron

Announced in the summer of 2010 at Musikmesse,^[1][2][3] the Monotron was Korg's first analogue synthesizer in two decades (the last design being the Trident mkII).^[4] Monotron is 12 x 7 cm, weighs approximately 100 grams (3.5 oz) and has a monochrome black-and-white design. It has a continuous ribbon controller for pitch and gate. The ribbon controller is also connected to the filter cutoff. There are five knobs for changing parameters.^[5] The synthesizer was designed by Tatsuya Takahashi.^[6]

The small form factor and analogue circuitry made some draw parallels between the Monotron and the Stylophone, a miniature analogue electronic keyboard musical instrument invented in 1967 by Brian Jarvis — British consumer electronics magazine Stuff called the Monotron "the new Stylophone" following its release.^[7]

Monotron has a voltage-controlled oscillator (VCO), voltage-controlled filter (VCF), a simple gated voltage-controlled amplifier (VCA) and a low-frequency oscillator (LFO).^[8] The VCO and LFO both use a sawtooth waveform.^[9] The Monotron's VCO has control over pitch and can reach frequencies below human hearing.^[8][10] The LFO has control over a range of <1 Hz to 900 Hz and can be routed to pitch or filter cutoff^[11] with control over intensity.^[8][10] The VCF is the same design as the Korg-25 filter chip that used on the MS-10 and MS-20 synthesizers.^[4][9] It has control over cutoff and resonance.^[5][8][10] External connections on the Monotron consist of a headphone output and an audio input.^[8]

Monotron Duo

The Monotron Duo was announced in November 2011.^[12] It was exhibited at NAMM.^[13] It shares the same base design as the original Monotron but is instead coloured blue. Like other models, the Monotron Duo has a ribbon controller (with a range of one octave).^[14] The ribbon controller has four playing modes: chromatic, major, minor and unquantised.^[15][16] Monotron Duo has an automatic tuning system to ensure tuning stability.^[17]

The Monotron Duo loses the LFO of the original and replaces it with an extra VCO and a cross-modulation circuit. The dual VCOs use square waveforms and have a range of four octaves. VCO2's frequency is dependent on VCO1 so it can be set to play in intervals. The cross-modulation circuit (named "X-mod" by Korg) is similar to the one found on Korg's Mono/Poly synthesizer.^[15][16] The 12 db/octave^[14] MS-20 filter is also present on the Monotron Duo with control over cutoff and resonance.^[17]

Monotron Delay

 

The Monotron Delay

Announced alongside the Monotron Duo, the Monotron Delay has a design more similar to the original. The Delay's faceplate is black and orange, with additional writing done in UV paint. Its ribbon controller is unquantised and spans four octaves.^[18][19]

The sound engine of the Monotron Delay includes a single VCO, an LFO, VCF and a delay circuit. The VCO uses a sawtooth waveform. The VCF is the same as the other Monotrons but only has control over cutoff.^[19] The LFO is connected to oscillator pitch and can be a triangle (blendable between sawtooth and ramp) or pulse (with PWM) waveform.^[20][16] The delay circuit is based on the PT2399 echo processor chip and has control over time and feedback.^[18] Maximum delay times are around one second. The delay will self oscillate at high feedback levels.^[19][15]

Modifications

 

Reverse of Monotron's printed circuit board (PCB)

Due to their accessibility, the Monotron series became popular candidates for modifications. Part of this popularity comes from Korg's decision to release the Monotrons' schematics online as well as labeling relevant solder points on the PCB.^[11]

Due to the lack of external connections on the Monotrons (apart from audio in/out), the most popular modifications add CV or MIDI capabilities to control the synthesizer from other hardware.^[21] Mods adding MIDI support use microcontrollers such as the Raspberry Pi^[22][23] or an Atmel ATmega328P.^[24]

Other modifications can be more extreme, like the "FrankenSynth". Nicknamed by the digital music resource site Ask.Audio, it is a heavily expanded Monotron designed in the United Kingdom by Harry Axten.^[24][25][26] Carrying out any modifications on a Monotron voids the synthesizer's waranty.^[19]

References

1. Álvarez, José Antonio (December 19, 2022). "Korg Monotron -el recuerdo del sintetizador en miniatura que impulsó el revival analógico en 2010". Future Music - SONICplug | Tecnología musical y sonido (in Spanish). Retrieved January 21, 2023.
2. The MusicRadar team (March 24, 2010). "Musikmesse 2010: Korg monotron is analogue ribbon synth". MusicRadar. Retrieved January 22, 2023.
3. "Korg debuts pocket-sized Monotron analog synth, and we want it (video)". Engadget. Retrieved January 22, 2023.
4. Scarthpublished, Greg (July 14, 2010). "Korg Monotron review". MusicRadar. Retrieved January 22, 2023.
5. "Korg Monotron". www.soundonsound.com. Retrieved January 15, 2023.
6. "Analog For The People: Synth Master Tatsuya Takahashi On Engineering Fun". WRVO Public Media. December 22, 2017. Retrieved January 22, 2023.
7. Grabham, Dan (August 31, 2021). "Korg Monotron is the new Stylophone". Stuff. Retrieved January 22, 2023.
8. "Korg - Monotron · Tech Review ⟋ RA". Resident Advisor. Retrieved January 21, 2023.
9. . Wired. June 17, 2014. Archived from the original on January 17, 2014. Retrieved January 22, 2023.
10. Beres, Ivan (July 23, 2010). "Review: Korg Monotron". TechCrunch. Retrieved January 21, 2023.
11. Castellano, Carlo (November 10, 2010). "Korg - Monotron Review". Age of Audio. Retrieved January 22, 2023.
12. Keene, Jamie (November 3, 2011). "Korg unveils the new Monotron Duo and Delay". The Verge. Retrieved January 21, 2023.
13. Billboard. Nielsen Business Media, Inc. January 7, 2012.
14. "Korg monotron DUO Testbericht: Analoger Minisynthesizer mit zwei Oszillatoren und Bandtastatur". delamar.de (in German). Retrieved January 21, 2023.
15. "Korg Monotron Delay & Duo". www.soundonsound.com. Retrieved January 22, 2023.
16. "Monotron DUO & Delay Review". MusicTech. Retrieved January 22, 2023.
17. Future Music (January 28, 2012). "Korg Monotron Duo review". MusicRadar. Retrieved January 21, 2023.
18. Future Music (January 28, 2012). "Korg Monotron Delay review". MusicRadar. Retrieved January 22, 2023.
19. "Korg monotron DELAY Testbericht: Putziger Analogsynth mit Bandtastatur & Delay". delamar.de (in German). Retrieved January 22, 2023.
20. Vail, Mark (February 2014). The Synthesizer: A Comprehensive Guide to Understanding, Programming, Playing, and Recording the Ultimate Electronic Music Instrument. OUP USA. ISBN 978-0-19-539489-4.
21. "This video makes it easy to mod KORG's ultra-cheap monotron for analog CV". CDM Create Digital Music. September 25, 2019. Retrieved January 20, 2023.
22. Ash Hill (September 19, 2020). "This Raspberry Pi Adds MIDI to a Korg Monotron Synth". Tom's Hardware. Retrieved January 20, 2023.
23. "Korg Monotron MIDI". The MagPi magazine. Retrieved January 22, 2023.
24. Fabio, Adam (June 9, 2018). "Monotron Gets All The Mods". Hackaday. Retrieved January 20, 2023.
25. Sethi, Rounik. "This Hacked Synth Is A Korg Monotron, But Not As You Know It". ask.audio. Retrieved January 20, 2023.
26. Rogerson, Ben (June 11, 2018). "This pimped Korg Monotron has been super-charged and turned into a two-octave keyboard synth". MusicRadar. Retrieved January 20, 2023.