Siaehv

The Siaehv is a traditional Romulan stringed instrument comprising thee arms joined together at one end, with three strings, one running along each arm. Each string is connected to a cylindrical resonator at the end of a bendable stick.
The name "Siaehv" is a shortened form of "sei u'aigre aehvsu", meaning "three and many voices".
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The instrument is played in a rather unique way. The playing hand pushes down on the string at the position of a note, while at the same time plucking it with a long plectrum. This causes the string to produce the desired note in the form of overtones.
Meanwhile, the other hand grips the string's stick and bends it, thus bending the note.
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The basis for the Siaehv is the Vietnamese Đàn bầu, a rather fascinating instrument. The idea of a "tripple dan bau" comes from Nicolas Bras' (aka "musique de nulle") video "My own version of the vietnamese dan bau".
In his version, all three strings are tuned to A. Maybe it's the same here, or maybe the tuning is different.