Music scroll button

When I go to my music player, the index scroll bar to the right used to be all letters, so it would show

: "A

   B

   C

   D

   E

   F

   G" and so on.. but now, I dont know what happened and it skips every other letter.It shows:

   "A

     *

    C

     *"

I want it to change back. What to do?