Provided are an electronic musical instrument, computer storage device, and method for generating tone. A sound source in an electronic musical instrument generates a first tone at a first pitch in response to a first tone generation instruction received by an input device of the electronic musical instrument. A second tone generation instruction is received to generate a second tone at a second pitch while generating the first tone at the sound source. A determination is made of a pitch difference of the first and the second pitches. The sound source is controlled to generate the second tone and to not generate the first tone in response to determining that the pitch difference does not exceed a predetermined number of tones. The sound source is controlled to generate the second tone in response to determining that the pitch difference exceeds the predetermined number of tones.