"Reverse Engineering 101: Buchla 700 as a Case Study" by Kweiwen Tseng (Taiwan)

  • Published on 10/08/2025 by kweiwen
buchla Ddsp frequency modulation juce phase modulation synth Synthesizer

This talk covers the reverse engineering of the Buchla 700, by tracing its firmware, decoding documents, and rebuilding its DSP algorithms. It follows the process from a PureData prototype to a JUCE plugin and Daisy hardware implementation, showing how digital archaeology can recreate legacy instruments. The Buchla 700’s design also informs modern neural audio synthesis, such as DDSP frameworks. The session features a PureData patch demo, plugin showcase, and modular hardware presentation.

The Buchla 700, released in the late 1980s, represents a unique moment in electronic music history, where a digitally-aided synthesizer was combined with an ambitious user interface design. It featured pressure-, position-, and touch-sensitive plates, control voltage receptacles, and SMPTE synchronization for external monitors. On the software side, beyond generating and modifying its polyphonic voices, it included preset storage, a score editor, and a sequencer, enabling users to transition between studio composition and live performance.

 

Additionally, it featured a highly flexible synthesis architecture with four oscillators and six indices, resulting in 12 topologies. Each routing produced different modulation behaviors, including Frequency Modulation (FM), Ring Modulation (RM), and Timbre Modulation (TM). Every oscillator and index could be controlled by an Envelope Generator, referred to in Buchla's terminology as a Function Generator. This design allowed users to program complex envelopes, even condition-based envelopes.

 

This lecture explores the reverse engineering process of the Buchla 700, covering original firmware, limited video footage, performance recordings, technical manuals, documents, and other developers' projects. It traces the workflow from early prototyping in Pure Data, reconstruction of the DSP algorithm using C++ and JUCE, and hardware implementation on the Daisy platform. We demonstrate how digital archaeology can recover lost designs and recreate a fully functional modern instrument.

 

In the age of neural networks, revisiting these vintage instruments is not merely nostalgic; it also offers valuable insight into differentiable sound synthesis. We will briefly demonstrate how Buchla 700's architecture can inform modern neural audio models, particularly within frameworks like DDSP, where interpretable synthesis structures are essential.