The Tone of Prime Unity Will Schrimshaw Figure 1: Preparations at La Cambre for an expedition around Brussels. • 2013 • Workshop /The Tone of Prime Unity/ was the title given to a workshop delivered at La Cambre, Brussels, as part of the Tuned City festival in 2013. The workshop was focused upon the prevalence of the 50Hz/60Hz hum in urban environments and the impact this has upon the habits of listening subjects. The workshop involved sound walks, field recording exercises and the fabrication of instruments for recording electromagnetic signals. The first day of the workshop was dedicated to a critical discussion of R. Murray Schafer’s work, in particular his concept of the tone of prime unity. The ideas discussed during the workshop at La Cambre and continued as we drifted throught the city in search of influential signals and keynote sounds are outlined in the essay below. My thanks to the workshop participants and Tuned City and Q-O2 teams for their thoughts and support. 1