For multi-instrumentalist Colin Schlitt, songs often begin in nonsense. After composing the music, he sings melodies made of little more than strung-together vowel sounds and syllables.

It’s “literal gibberish,” placeholders waiting for his subconscious to supply words that fit the phrasing. “Eventually, the real lyrics sort of reveal themselves,” he said. Mr. Schlitt learned the trick from a bandmate in the long-running group El Radio Fantastique, where he plays bass. (The approach was also used…