Noun

• S: (n) descant, discant (a decorative musical accompaniment (often improvised) added above a basic melody)

Verb

• S: (v) descant (sing in descant)
• S: (v) yodel, warble, descant (sing by changing register; sing by yodeling) "The Austrians were yodeling in the mountains"
• S: (v) descant (talk at great length about something of one's interest)