The singer always vocalizes a few notes to warm up before practicing.

vocalizes 是动词 vocalize 的第三人称单数形式。vocalize 由词根 vocal（声音的、发声的）加上动词后缀 -ize 构成，意思是"发声、哼唱"，特指用嗓音发出声音但不一定唱出具体歌词。