thundermuffin37 • Oct 6, 2018 So I know violin is a C instrument and alto sax is an e flat but what is viola? Comments [user=24383921]Kenobiingondolin2019[/user] It's a C instrument. Your stringed instruments (Violin, viola, cello, double bass) are all in the key of C, as are piano, harp, guitar, and others. [user=28678198]Victoria Hoy Andrus[/user] Also a C instrument. The clef is alto clef, which is a movable clef. When viola uses it, the middle line is C. Like, the clef points to the C, and the clef sign is centered on the staff, if that makes sense. Your comment Only members of a group can post to group discussions, so Join What type of instrument is viola?