Viola
The viola was an Earth musical instrument, bigger than a violin and smaller than the cello and double bass.

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

In 2370, Juliana Tainer played the viola part accompanying Data's performance of a piece by Georg Friedrich Händel. ()

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Earth musical instruments