Viola

The viola is an Earth musical instrument, bigger than a violin and smaller than the cello and double bass. It serves as the middle voice of the violin family.

A male Vulcan viola player was among the musicians at a string quartet recital in Ten Forward in 2366 that also featured Lieutenant Commander Data on violin and Miles O'Brien on cello. 

Data's mother Juliana Tainer played the viola part accompanying Data's performance of a piece by Händel.