HARD-2500

MIDI modulation matrix inspired by the ARP 2500

Max/MSP

https://github.com/rennyhyde/HARD2500

Class project for MUSI 6003: Music Technology History & Repertoire

Historical Background

The Arp 2500 is a legendary analog synthesizer developed in the early 1970s by ARP Instruments.Taking their name from founder Alan R. Pearlman, the ARP 2500 was designed by Alan Pealman, David Friend, and Lewis Pollock. Looking to expand upon Robert Moog’s design,  the ARP 2500 positioned itself as one of the most sophisticated synthesizers of its time. Unlike Moog oscillators, Pearlman’s oscillators did not overheat and drift out of tune. Furthermore, the ARP 2500’s interface was groundbreaking. Through a unique matrix system, the ARP was not physically patched like other early modular synthesizers. This matrix system laid out all possible connections between each module, giving musicians unprecedented control over their sound without reliance on patch cables. However, this matrix system was often difficult to debug and prone to cross talk between channels. Less than 100 ARP 2500s were sold. 

Technical Details

The matrix works based on sliders, so as you move it to the desired channel the desired channel, you move through alternate routings, which might reveal an interesting and unanticipated result.

There are 6 waveshapes available: sine, square, saw, inverse saw, weird spliced saw, and random. The "weird spliced saw" is an erroneous attempt at making a triangle wave, but I decided to keep it since it was a pretty interesting shape.

In terms of the patch itself, it's (conceptually) very simple: Depending on the position of an oscillator's slider, the oscillator is sent to a particular MIDI CC channel. It's added to any other oscillators on that channel, and then the scale and offset are applied.

In practice, the routing was extremely complicated. Had I known about gen~ the process would have been much easier, but the tedious manual routing worked fine.