Webster's Revised Unabridged Dictionary · 1913

Vocalize

Vocalize (vō"kal*īz) , transitive verb

[Compare French vocaliser.]

1.
To form into voice; to make vocal or sonant; to give intonation or resonance to.
It is one thing to give an impulse to breath alone, another thing to vocalize that breath. — Holder
2.
To practice singing on the vowel sounds.