From Longman Dictionary of Contemporary Englishkeyboardistkey‧board‧ist /ˈkiːbɔːdɪst $ -ɔːr-/ noun [countable] someone who plays the keyboard
Examples from the Corpus
keyboardist• Just ask Luscious Jackson keyboardist Vivian Trimble.• Trumpeter Barbaro Teuntor Garcia is the only horn player; there is no keyboardist.• The rhythm section of these hits then began cutting behind the poorly shouted vocals of a white keyboardist named Harry Casey. 