Membership of health and fitness clubs in the UK has grown rapidly since the early 1990s. Recent estimates suggest that there are around 4.5 million members of private health clubs in the UK, or 9 per cent of the adult population, compared to 6 per cent at the start of the new millennium and a fraction of the population in the early 1990s. The estimated value of the sector is £3.7 billion, with nearly six thousand clubs operating in the UK (Mintel 2005; FIA 2008). However, the era of spiralling membership levels and club openings has come to an end in recent years. In response, health and fitness club operators have switched their emphasis to increasing the productivity of existing estates. As a result, they are now devoting more resources to the retention of existing members than simply signing up new recruits (FIA 2003). This has led to a host of management initiatives designed to ensure that newcomers are quickly embedded as club members. These include: group inductions to introduce new members to those who joined at about the same time; appointments to devise exercise programmes; regular reviews of progress in the first few weeks of membership; free personal training sessions; social events; and group exercise classes, often promoted through taster sessions and in-club marketing. These group exercise classes – known as exercise to music (ETM) – are the focus of this chapter.