These compositions were determined by the traffic flow on an eight-lane section of Interstate 5. Each lane was designated a consecutive note in an octave. When a vehicle traveled past a specific point in that lane, it triggered the sound of that note. The lowest note in each composition starts on the outside lane of south-bound traffic. The highest note is on the outside lane of north-bound traffic. The four compositions each represent ten different minutes of traffic flow.
9:00am on a Monday (in B major) = 1,589 notes/vehicles
12:00pm on a Tuesday (in C minor) = 899 notes/vehicles
5:30pm on a Wednesday (in E major) = 1,065 notes/vehicles
1:00am on a Thursday (in F minor) = 506 notes/vehicles