scat singing vs vocalizing

scat singing and vocalizing both are nouns.

Word	Noun	Adjective	Verb	Adverb
scat singing	Yes	No	No	No
vocalizing	Yes	No	No	No

As nouns, vocalizing is a hypernym of scat singing; that is, vocalizing is a word with a broader meaning than scat singing:

scat singing: singing jazz; the singer substitutes nonsense syllables for the words of the song and tries to sound like a musical instrument
vocalizing: the act of singing vocal music

Other hypernyms of scat singing include singing, jazz.

scat singing (noun)	vocalizing (noun)
singing jazz; the singer substitutes nonsense syllables for the words of the song and tries to sound like a musical instrument	the act of singing vocal music