Why do we say chant, but not sing?

Expressions researched:
"Why do we say chant, but not sing"

Bhagavad-gita As It Is Lectures

It is same thing. Either you sing or chant, the same thing.

Lecture on BG 2.13 -- Public Lecture With German Translation Throughout -- Hamburg, September 10, 1969:

German guest or devotee: Why do we say chant, but not sing?

Prabhupāda: It is same thing. Either you sing or chant, the same thing.