The calm of an afternoon music class in a four-story building in Tokyo's central Yutenji district is ever so slightly disturbed by the noise of cars on the street outside. But the five students there appear entirely unconcerned as they keenly strain their ears to the sparkling melodies of "Edelweiss" performed . . . by whistling.

Kimiko Wakiyama whistles to a ukulele accompaniment, using vibrato and dynamics as freely as if her lips were a violin and her tongue its bow. But Wakiyama, the instructor of the whistling class, is no mere playful oral puckerer; in fact she was women's champion at this year's International Whistlers Convention in April in North Carolina.

"We start by practicing breathing," she says after the demonstration, as she moves toward the mirror wall. Students stand there, look at their reflections, and learn how to breathe by closely observing their bodies — especially their lower abdomens. To produce a long and beautifully modulated whistling tune, having deep "abdominal breathing" is a key, Wakiyama explains — as Peter Bjorn And John's "Young Folks" provides BGM.