Harmonic Singing is my term for singing chord arpeggios.

Harmonic Listening is better known as "taking harmonic dictation."

To increase your ability to identify harmonies--or chords--

learn to sing chord arpeggios. Sing them in tune, and sing them fast.

The goal is to hear the individual tones of a chord all at once.

The links below will help you sing and identify harmonies in real musical excerpts.