Pi-Stomp hardware running MODEP (Image by Author)

Neural Network Guitar Plugins on Pi-Stomp with MODEP

Keith Bloemer


One of the coolest devices for technically minded musicians is the MOD-Duo from MOD-Devices. Not only is it a standalone audio processor with 300+ built in audio/MIDI effects, but it also acts as a server that you can interact with through a browser to build any kind of pedalboard imaginable. The sheer number of possibilities on these devices (now upgraded to the MOD-DuoX and most recently MOD-Dwarf), is daunting, but it has the power to revolutionize how people make music.

What does this have to do with neural networks? If you are familiar with my work on GuitarML, you know that I develop guitar plugins that use neural networks to mimic analog amplifiers and pedals. I feel lucky to have come along at an interesting time in computing tech, where there is both an abundance of open source software and a surge in practical A.I. applications. After creating a couple of audio applications for desktop computers, I became interested in running my software on embedded devices.

One of the remarkable things that MOD-Devices has done for the Linux community is to open source the software running on the MOD-Duo. This allowed others to come along and create popular DIY project-pedals such as Pi-Sound, which runs the MOD virtual pedalboard on a Raspberry Pi 3. It also allowed developers like me to add their own creations in the form of LV2 plugins. I had created a pedal-like device that runs my neural plugins before, but it needed a lot of work to build it into something I could Velcro on my pedalboard and play gigs with.

My pedalboard (Image by Author)

Enter the Pi-Stomp. This is a fully featured DIY guitar stomp-box with an LCD screen and multi-knob interface, which costs just over $200 with the enclosure and optional add-ons. Built on the Raspberry Pi 3, it runs MODEP (a MOD-Duo emulator) which acts as the server for the virtual pedalboard. The best way to explain how this works is to show it. This is a demo of the Pi-Stomp running the virtual pedalboard, along with my own GuitarML plugins that use neural networks to mimic a popular guitar pedal and amp.

(Video by Author)

This short demo just scratches the surface of what you can do on the virtual pedalboard, and it’s not just for guitarists. Using a MIDI connection, one could access any number of synths or keyboard style effects.

Porting my existing plugins to run on a MODEP device was took some trial- and-error, but it was not overly complicated. The tools needed to do this are in the mod-plugin-builder project on Github. My own creations shown in the video are available here, with an example build process in the plugin Readme. Using a modified build process with the MOD-Duo/MOD-DuoX/MOD-Dwarf as the target, one could compile and run my plugins on official MOD devices as well.

The amount of DIY electronics required to build the Pi-Stomp may drive away the average musician, but for anyone with the slightest interest in learning, the result is well worth the effort. For audio developers, this is a dream machine for making anything you can think of a reality.

I hope you enjoyed reading this article! For questions and feedback you can email me at smartguitarml@gmail.com.

GuitarML plugins on the MODEP virtual pedalboard (Image by Author)