On the sound powers of flute combination tones produced by singing while playing

“Singing while playing” is an extended flute technique that can produce weak, but audible, combination tones that are heard along with the note being sounded on the flute and the note that the player is singing or humming. The present work was motivated by an interest in obtaining a quantitative understanding of the factors determining the sound powers of these combination tones in hopes of making them louder and/or more audible. The tones under study were produced in a conventional flute powered by an artificial blower apparatus whose pressure/flow could be modulated at audio frequencies (by a speaker connected to the gasline) to mimic player singing. While quantitative results were elusive, one takeaway finding was clear: the combination tones are loudest when they have a frequency that aligns with one of the flute’s passive resonances, a situation which can be facilitated with the use of forked fingerings that preserve the strength and position of the resonance used for the sounded flute note while shifting the positions of the unused resonances so that one of them better coincides with the frequency of the desired combination tone.