when master Ebrahim Ghan bari Mehr performed som corrections on the Robab to increase its entent of sound and the ease of playing, (installation of finger board, seHing the metallic frets, reducing the width and thickness of the neck)
According to the reeds of players, the problems which they referred to in the Robas of that time, and evaluation and study of the folke Robabs, a set of conversions and corrections performed to access to the better quality of sound which will be approximately the same as original sound, and to make playing Robabs, an easier task. These changes are:
1- Since this is basically abass instrument with high volume of sound; So, a grid was installed in the distance between the finger board and the place where the skin will be attached. Pattern of the grid ofter making some versions is as you can see in the figures.
2- To fur ther increase the extent of the Robab sound, a pattern prepared that according to it, tinger board extents to the outset of the place where the skin will be altached. In this pattern the extent of the Robab sond with three melody string ( main chords) is approximately 2.5 octaves and this extent in the Robabs with 4 melody strings is approximately 3 octaves
3- To make playing the Robab easier, Master ghan bar mehr reduced the length of Robab bowl (the part where drone pege are set on it) and to the some amount increased the length of the neck. In this situation 7 drone pegs installs on the bowl; so, to increase the drone pegs to 13 for Alto size, and 15 for shah-Robab (bass size), pegs were set in two rows.
4- To mke playing easier, a wooden piece with especial form is installed in the place where the arm is in contact with the edge of bowl.