Adam Clarke on 1 Chronicles 15:21

On the Sheminith - According to the Targum, this signifies an instrument that sounded an octave, or, according to others, an instrument with eight strings. The Syriac and Arabic have it, instruments to sing with daily, at the third, sixth, and ninth hour; the Vulgate, an octave, for a song of victory: some think the eighth band of the musicians is intended, who had the strongest and most sonorous voices; and that it is in this sense that shelomith and lenatstseach should be understood.