The idea of using a simple app to time the performance of Finn Mortensen’s Sonate für zwei Klaviere, op. 26, came from the practical problems with timing the transitions from one field to another. The prescribed method of practising with a stopwatch until you develop a feel for the approximate durations seems most appropriate when you always perform the piece with the same durations. However, since we performed and recorded the piece with several different durations on several occasions, we found we needed a more accurate method.

At the heart of the app is a simple timer function, counting down each field and immediately starting counting down the following field when time is up on the previous one. Before the performance, the performers choose the piece’s duration between the options full version (the duration given in the printed score), half version (the shortest permitted in the composer’s instructions), and three-quarter duration. In addition, the app has the option of a version where the fields are getting gradually shorter to get more exponential dynamic development. Finally, the app also lets the performers choose the duration of the initial countdown in five-second intervals from five to thirty seconds.

The app also includes a random chord generator for the sixth field, which, by tapping the screen, will give one of the 24 chords at random, similarly to spinning the wheels in the score, but immediate and easier readable. This part also has a practice mode with only the chord generator and the timer for the sixth field. 

The code for the app has been uploaded to GitHub.