This piece of music features two players and two instruments. One plays the Santur, while the other plays the Tombak. They are purely improvising. The Santur started to play first and then the Tombak built a beat off the Santur’s melody. The tempo and rhythm change often, as there are many starts and stops in this 16-minute clip. Improvisation on the Santur by Dariush Saghafi, and the Tombak is played by Jahangir Mohammadi. I found this recording on YouTube.