Lawrence Button

Lawrence is a US-based pop-soul group founded by siblings Gracie and Clyde Lawrence, who have played live alongside innumerable collaborators such as Vulfpeck, Jon Bellion, Jacob Collier, the Jonas Brothers, and the Rolling Stones. Their impressive live show has no timed playback unlike most modern pop acts; instead they aim to produce every sound live on stage.

There are a few specific samples, one-shots and musical interludes which are pre-recorded, and they wanted to have a very obvious visual way of showing the audience that these were played in the moment. I was commissioned to design and build an instrument that would showcase these samples and be obvious to the audience, even in the 10,000+ capacity venues the band often play in.

Design

We went through various design iterations, finally settling on a simple giant 36cm wide button (just large enough to fit inside a Pelican 1637 Air case). It has a 20cm deep base, which houses 768 individually addressable ultra-bright RGB LEDs on flexible PCBs, and the control electronics. I wanted the LEDs to be visible from as far around as possible (if playing in a venue with audience on all sides).

Building the button to withstand the rigours of touring (while also being lightweight enough to be checked into hold luggage) was a challenge. The top and bottom plates were CNC machined out of 4mm aluminium, and a custom 3D-printed middle part with M3 heat-set inserts held them together. The middle part has a profile with grooves for cables and to hold the flexible LED PCBs, revolved to an angle of 240 degrees. The LEDs are a few centimetres back from the edge, where a diffuser (made of 3mm translucent acrylic, heated up and bent around a custom CNC’d mould of the correct diameter) fits in a groove to give the impression of one coherent light source. The dome is spun out of 2mm aluminium on a custom 400mm dome mould, welded to another piece of aluminium and a 3D-printed adapter screwed on to attach to the switch mechanism

This leaves a small enclosure inside for the control electronics, power supply, and push-switch mechanism.

The mechanism itself took a while to perfect. The button top needs to come off for transport, but also needs to be sturdy enough not to fly off when hit hard. The first iteration (with a smaller button) had a custom-printed mechanism with four springs and four retaining magnets to give the correct force/travel curve (the magnet gives a simulacrum of a dome switch with some ‘give’) and the revised version, with a larger button, allowed for four giant Cherry MX switch copies with a custom spring to give more upwards force (the dome weighs almost 1kg).

Electronics

The first iteration of this board had a custom STM32-based sample playback PCB, which would play out 48KHz WAV files on an SD card, and sample-synchronously read back from a text file with hex codes to display on the WS2812 LEDs. The PCB had a daughterboard with two 7-segment displays and buttons to select samples and stop the audio. The PCB was quite space-constrained and also featured XLR line drivers and phantom power fault protection, so all components were surface-mount.

The second iteration was a different design – the band now tours with a dedicated Ableton rig and video wall / lighting rig, so the decision was made to offload audio playback onto Ableton, and output MIDI / input DMX512 to the button to use as a conventional lighting fixture, giving the LD control of colour and intensity. A custom PCB was made to house two Arduino Nanos, one taking care of DMX to WS2812 with optoisolated MAX485 line drivers, and the other a standard DIN MIDI output with noteon/noteoff every time the button was pressed.