Based on data taken from Billboard Magazine's R&B/Soul Singles charts. Along with the artists themselves, I've listed two songs apiece that I feel represent their recorded '70s output.
RYM Ultimate Box Set > Disco Re-Edits / Disco House - Rate Your Music
15 Songs That Shook New York's Queer Dance Floors in the 1970s and
100 All Time Classic Dance Hits Of The 1970s (1988, CD) - Discogs
Every No. 1 song of the 1970s ranked from worst to best
The 100 Jazz Albums That Shook The World
Every No. 1 song of the 1970s ranked from worst to best
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Funk Songs 70s, The sound of Japan's City Pop scene preceded the even sunnier sounds of J-Pop, with a sound that drew from so many sources.
100 Greatest Classic R&B/Soul Songs
Hiring a 70's Disco and Funk band : A Complete Guide