MIDI Keyboard Defined DJ Performance System Christopher Dewey University of Huddersfield Queensgate, Huddersfield West Yorkshire, United Kingdom c.dewey@hud.ac.uk Jonathan P. Wakefield University of Huddersfield Queensgate, Huddersfield West Yorkshire, United Kingdom j.p.wakefield@hud.ac.uk Matthew Tindall University of Huddersfield Queensgate, Huddersfield West Yorkshire, United Kingdom m.tindall@hud.ac.uk ABSTRACT This paper explores the use of the ubiquitous MIDI keyboard to control a DJ performance system. The prototype system uses a two octave keyboard with each octave controlling one audio track. Each audio track has four two-bar loops which play in synchronisation switchable by its respective octave’s first four black keys. The top key of the keyboard toggles between frequency filter mode and time slicer mode. In frequency filter mode the white keys provide seven bands of latched frequency filtering. In time slicer mode the white keys plus black B flat key provide latched on/off control of eight time slices of the loop. The system was informally evaluated by nine subjects. The frequency filter mode combined with loop switching worked well with the MIDI keyboard interface. All subjects agreed that all tools had creative performance potential that could be developed by further practice. Author Keywords DJ, Electronic dance music, performance, exploration CCS Concepts • Applied computing → Sound and music computing; Performing arts; • Human-centered computing → Interface design prototyping; 1. INTRODUCTION Electronic Dance Music (EDM) DJs characteristically blend and sonically manipulate two or more audio tracks to produce a seamless output of audio content. Traditional DJ systems typically feature two vinyl turntables and simplified audio mixing interface which enable the DJ to beat-match, cue and crossfade between sound sources and manipulate spectral characteristics of the sources [10]. DJ systems have evolved to also include virtual and hybrid solutions [8]. Hybrid systems enable DJs to use familiar traditional gestures [4]. Modern virtual systems extend the range of tools for sound source manipulation and musical expression. The discipline of controllerism emerged in the mid-2000s. Moldover undertook bespoke hacking of MIDI keyboards to facilitate his EDM performance practice [7]. EDM DJs currently utilise a variety of commercial Music Production Centres/Workstations (e.g. Akai MPCs and Ableton Push). Recent research has mainly focussed on extending the sonic manipulation capabilities of hybrid system by using traditional interaction gestures to control new types of parameters [1,3-5]. This paper takes an alternative approach, as adopted in the development of “ColorDex” [9]; which replaced the audio faders found on a DJ mixer with a hand held cube, and considers a simplification of the virtual DJ system interface. This work replaces the hardware interfaces used by EDM DJs with the piano keys of a two octave MIDI keyboard controller and explores using this interface for time and frequency manipulation of EDM for use in loop-based DJ performance. 2. MOTIVATION The motivation to use only the piano keys of a two octave MIDI controller as a virtual DJ system interface was: 1) Democratisation - MIDI controller keyboards are more widely available and affordable than hardware interfaces in commercial virtual DJ systems. Knobs, pads and faders which vary between controllers were excluded. 2) Playability - Inspired by Atlantic Records engineer Tom Dowd who enabled mix engineers to “play the faders like you could play a piano” by replacing the mixing console’s large rotary knobs with slide-wire faders [2] providing an “affordance of music playability” [6]. 3) Reductionism – To explore whether a simpler, easier and more accessible user interface can be created and to see if this has the potential to lead to new creative possibilities. 3. DJ/EDM TECHNIQUES The following observations were made based on informal analysis of YouTube performance videos and the authors’ experience. DJs use predefined cue and loop markers to jump seamlessly between different sections of audio tracks. Faders are used to alter the level of "beat-matched" audio tracks to move seamlessly between tracks or to blend tracks. Peaking parametric filters are used to carve out specific frequencies. Low pass, high pass and band pass filters are also used to isolate specific frequencies or to sweep through frequencies. These three techniques are used sequentially, independently or in combination to realise a musical intention. EDM production involves the creation and manipulation of repeating and varying loops at the micro and macro level. At the micro level, step sequencers are commonly used to create rhythmic and/or melodic patterns using oscillators and/or samples of pre- recorded audio material. At the macro level these patterns are sequenced and combined to create tracks either in a fixed sequence or dynamically performed in a live setting. 4. IMPLEMENTATION The prototype interface was implemented using HTML5, JavaScript and the WebMIDI and WebAudio APIs (see Figure 1). Each octave controlled one of two audio tracks as the ability to control at least two audio tracks simultaneously is a fundamental characteristic of any DJ system. Given more octaves this is extensible to control more tracks. The system ensured all audio elements were synchronised and looped continuously. It appeared logical to use the inferred visual division afforded by the layout of the black keys on the interface. The first four black keys of each octave were used to switch between four different looped sections of the two audio tracks. This macro-level switching tool was inspired by the common practice of setting cue and loop markers. In contrast to commercial systems the switching of the two bar loops occurs at the current point in time of the loops. The white keys were used to manipulate the audio tracks in either the time or frequency domain. The highest key (C3), shaded in grey in Figure 1, toggles between the two modes.