Answer: Kotos; shamisens; heterophonic
Explanation: This is a Hogaku concert which is a traditional concert of Japanese traditional music. It is a concert consisting of several parts and featuring musicians dressed in traditional Japanese costume. In doing so, musicians take certain instruments in a particular part of the concert they play, so that when the second part of the concert begins, the musicians replace the instruments they play. All the instruments played by musicians are on the floor from where they pick them up when they need to play a specific instrument for a particular part of the concert.
The said kotos is an instrument that musicians play in the first part of the concert. It's a stringed instrument - a zither with thirteen strings and the ensemble in that section has three kotos. In addition, the ensemble has three aforementioned shamisens and that is three-stringed lutes played with a plectrum. During the playing of these instruments, musicians who are both men and women also sing, where, as stated, all the parts appear to have the same melody, but each of these components has a somewhat different mode, which gives a heterophonic texture overall.
