One who is an expert in or has a keen sense of rhythm.(noun)
Music One who studies or produces rhythm.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "rhythmist" in a sentence
"As a rhythmist, my story starts with the beginning of time and space, which was the big bang, when the blank page of the universe exploded and created the stars, the planets, the sun, the moon, earth, and us."
"To the metrist and rhythmist the poem will be of interest from the first, and throughout."
"Their drummer is most definitely my favorite female rhythmist (word?) since Janet Weiss."