Appropriate bass and treble give people a pleasant and comfortable feeling, but if bass is always the main pitch, it will give people a feeling of depression. Similarly, if treble is always the main pitch, it will give people a feeling of high pitch, but always listening to the same pitch will be monotonous, and only the combination of high and low tones can give people pleasure. So music is a combination of different highs and lows. Singing is the same, even if the high-pitched or low-pitched singer sings a song from low to high, with ups and downs, to interpret the emotions in the song. Because everyone's voice is different, even if they are tenors, sopranos, basses and contraltos (although there are fewer singers in this range), they give people different appreciation feelings because of different timbres.