We present Patchwerk, a networked synthesizer module with tightly coupled web browser and tangible interfaces. Patchwerk connects to a pre-existing modular synthesizer using the emerging cross-platform HTML5 WebSocket standard to enable low-latency, high-bandwidth, concurrent control of analog signals by multiple users. Online users control physical outputs on a custom-designed cabinet that reflects their activity through a combination of motorized knobs and LEDs, and streams the resultant audio. In a typical installation, a composer creates a complex physical patch on the modular synth that exposes a set of analog and digital parameters (knobs, buttons, toggles, and triggers) to the web-enabled cabinet. Both physically present and online audiences can control those parameters, simultane-ously seeing and hearing the results of each other’s actions. By enabling collaborative interaction with a massive analog synthesizer, Patchwerk brings a broad audience closer to a rare and historically important instrument. Patchwerk is available online at http://synth.media.mit.edu.