The performing arts are temporal arts. Experiencing dance, music and theatre is a dynamic process that occurs over time and is often shared between groups of people. The continuous and collective nature of the experience of any live performance poses unique challenges to a quantitative or neuroscientific approach to audience research. This chapter reviews the latest methodological approaches and techniques to quantify audience engagement in real-time and across multiple spectators. Three levels of real-time measures of audience engagement are discussed, including continuous behavioural, psychophysiological and brain signals. All three levels can be used to measure what spectators do and feel – both individually and collectively – with a view to providing insights into the neurocognitive mechanisms that are at play when people engage with the performing arts. These measures complement, rather than substitute, traditional methodologies such as qualitative interviews, questionnaires, audience observation and phenomenology. The chapter discusses the chances and challenges of these new audience research tools and reviews key studies that employ these methods across a range of performance situations.