The phrase "a smooth tone" is correct and usable in written English.
It can be used to describe a pleasant, even, or soothing quality in speech, music, or writing.
Example: "The speaker's delivery was captivating, characterized by a smooth tone that kept the audience engaged."
Alternatives: "a gentle tone" or "a mellow tone."
Mr. Huang, who won the prestigious Naumburg competition last year, plays with a smooth tone and a sleek and powerful technique.
Prokofiev's Second Violin Concerto opens with a solo line that poses an immediate challenge, not so much technically as interpretively: it demands introspective lyricism and a smooth tone at first but gradually sheds those qualities as it moves toward a steelier, more acidic sound.
Generally, these areas present a smooth tone, which is intensified in areas of greater usage and handling (such as the lower right corner).
They are comfortable to the left hand and give a smooth tone when amplified.
Mr. Clayton plays bass with a big, smooth tone and his band likewise gives off a concordant hum; Mr. Marsalis is a trumpeter who loves using mutes and brass vocalizing effects, and his band crackles and chatters in your ear.
His 1950s recordings were characterized by a light, smooth tone and rhythmic complexity; on occasion the intricacy of his rhythmic conceptions clashed with his precise timing and advanced technique.
Make sure you have a nice, smooth tone, and have fun with it!
Bermel brought a tangy, Gypsy-like style to his solos in the Adagio, drawing closer to Brahms's gruff spirit than clarinettists who fetishize a smooth, mellow tone.
There was Tory-bashing, during which his smooth tone ascended to a growl.
A smooth, pure tone calls for supple vocal cords.
The strings, particularly, played with a smooth, rounded tone.
