ABCs Of Vocal Harmony by Howard Austin/Elisabeth Howard. Ultimate sight-singing method & ear-training course + harmony. Two 90-minute tapes/book/case. Published by Vocal Power (VP.BTS-HD).
Scales \| Intervals \| Chords \| Rhythm & Meter, sharpen your sense of pitch, sing harmony, fill in the missing voice exercises, Takes the singer on a systematic journey to musical literacy - Journal Of Singing.