VAW / PRISM / Performance Restoration / RETROSPECTIVE MIXING
Music Technology
Research & Development
About the researcher
Bill Evans, PhD
Evans is an audio scientist, engineer and music producer. He studied at the University of Glasgow and Manchester Metropolitan University. He has developed and deployed technology for dozens of iconic artists, including his own band, Flying Colors.
INTRODUCTION
“Bill Evans is a brilliant audio scientist who creates highly innovative and genuinely musical software solutions to some of recording’s most vexing issues.” —Bob Ezrin (2025)
SELECTED Research
Virtual Audio Workstations
Virtual Audio Workstations are a natural evolution of DAWs within the context of gen AI, spatial computing, and tangible interfaces
They are a reimagining of DAWs, evolved into the virtual realm—a natural evolution of DAWs within the context of gen AI, spatial computing, and tangible interfaces.” VAWs are based on Dr. Evans’ alternate PhD thesis, Belexes: A Virtual Audio Workstation (2015). The submission included a hardware VAW designed and built by Evans, down the circuit boards.
Evans received a KEIF grant from MMU to develop the system’s tangible interaction system—the Volumetric Haptic Display. The VHD was the world’s first 3D force-projection system, used to create the VAW’a tangible interaction. It was complimented with a custom-designed 3D variable capacitance sensing system, provided high-precision, simultaneous spacial tracking of all fingers.
The workstation projected 3D imagery to display the systems visual components, employing head and eye-tracking to update the visual perspective in real-time. An alternate visual interface, using an early version of Microsoft’s first Hololens, provided the first virtual audio editing environment. The interaction model for the VAW was digital clay, wherein users can shape and mould audio, directly.
01
Retrospective Mixing
A suite of tools allowing the primary conditions and aspects of acoustic drum recordings to be altered after-the-fact. The processing is performed without replacing the original audio. Elements include tuning, acoustic space, microphones and their placement, and head/cymbal tension. The
instruments themselves can be changed, and their acoustic properties altered. First deployed by Evans to engineer drums on a commercial recording featuring drummer Marco Minnemann.
02
PRISM
PRISM is the world’s first system for perceptually-lossless conversion of acoustic recordings to event-based data (i.e., MIDI) data. In this form, music can be parsed as hierarchical grammar (e.g. ), and can be processed with LLMs without incurring audible artefacts or musical errors. As of 2024, a prototype AU/VST plugin is available for demonstration.
03
Performance Restoration
This methodology aims to restore musicians’ original intentions in recorded performances, as opposed to contemporary practices of “fixing mistakes”. Evans’ 2018 Manchester Metropolitan University PhD thesis included submission of the Flying Colors concert film, Live at the Z7.
Thesis (PDF) from Manchester Metropolitan University
04
Performance Synthesis
A group of technologies and methodologies to synthesis authentic human performances from specific artists. Evans will debut the technology in a forthcoming movie by Academy Award winning director I’ve just been told I can’t say who or anything else until the movie is announced.
05
Spectral Audio Clarity
A set of processes and techniques to increase the clarity of audio tracks, by targeting both physical (sonic) and cognitive auditory phenomena. Evans debuted the technology on Flying Color’s Live at the Z7. As per Wikipedia: “Critics place it among the best-sounding live albums ever made.”
06
Perceptually Lossless AI
Evans created several perceptually-lossless systems for commercial projects. They included artefact-free vocal isolation for Alice Cooper, and a time-shifting algorithm for a song featuring Steve Vai.
belexes vaw / PRISM
PRISM VIDEOS
PRISM debuted in 2015 with the release of the concert film, Live at the Z7. Since then, it’s been used with dozens of prominent artists (Alice Cooper, Deep Purple, Steve Vai) and in Hollywood films. Its existence was not fully-disclosed until 2024. Please note that videos have no advertising, background music or narration.
PRISM v2: Loop Editing
A traditional audio drum loop is translated to MIDI. Using features of PRISM’s Performer and Transformer system, the performance and sound are edited independently.
PRISM v2: Editing with Artificial Constructs
In addition to PRISM’s Retrospective Engineer methodology, PRISM features audio transformations that, while impossible in the real world, evolve contemporary audio engineering practices. This video demonstrates several examples. Drums by Mike Portnoy.
PRISM v2: Editing with Natural Constructs
PRISM isolates performances from their recordings. This enables Retrospective Engineering—going “back in time” to edit the initial conditions (e.g. instrument setup, room acoustics, microphones, tuning) of a recording—instead of traditional mixing (i.e., attempting to alter the results). Drums by Mike Portnoy.
PRISM v1: Audio to MIDI to Audio Translations
A deep dive into PRISM’s technologies for lossless conversion of audio to MIDI, including phase-accurate prediction of theoretical audio. The example song is from PRISM’s use on “Dreamers” from Legacy Pilot’s 2018 release, Con Brio. Drums by Marco Minnemann.
Note: This video includes extended audio examples and long-form text. It includes embedded buttons to skip ahead—however, this feature requires Vimeo Enterprise, so the buttons are unresponsive. Instead, our dedicated server hosts the interactive version, which also includes UHQ video and sound. This requires substantial bandwidth, and depending on server load, you may need to view the standard Vimeo version.
https://vimeo.com/manage/videos/1072570532
PRISM v1: Introduction to PRISM
A 3-minute introduction to editing MIDI translated from audio. Drums by John Ferraro and Chad Wackerman.
Evans with longtime creative partner, Thomas Price.
Steve Vai ▪ Steve Morse ▪ Mike Portnoy ▪ Neal Morse ▪ Alice Cooper ▪ Jay Graydon ▪ David Foster ▪ Van Romaine ▪ Albert Lee ▪ Sterling Ball ▪ Joe Bonomassa ▪ Steve Lukather ▪ Angel Vivaldi ▪ Chad Wackerman ▪ John Ferraro ▪ Marco Minneman ▪ Jim Cox ▪ Steve Lukather ▪ Crosby, Stills & Nash ▪ Peter Frampton ▪ Peter Collins ▪ Ken Scott ▪ Bob Ezrin ▪ Michael Brauer ▪ Mark Neeham ▪ Howie Weinberg ▪ John Petrucci ▪ Albert Lee ▪ Nick D’Virgilio ▪ Deep Purple