The Platters were one of the pre-eminent black groups of the 1950s, mixing doo-wop styles with pop; their soaring, elegant vocals taking a different path from earthier cousins like the Clovers and the Coasters. The Platters may have been the only such group to include a woman singer, Zola Taylor, in the traditional doo-wop male harmonies.
It's probably too limiting to label their music as doo-wop -- they wove tapestries of vocals and melodies into a style that broadened their appeal. And Reed's booming bass vocal lines highlighted many of their classic hits.
Here's a nice remembrance from the Los Angeles Times.
And here's a version of "My Prayer," in which Reed contributed the distinctive opening lines: