Daughter had 5 BMs and two sets of FGs/ RBs, and both of us moms walked in to the same song as the wedding party, Here Comes the Sun. (So, one song was more than enough for 9 pairs/individuals to walk down a 50’ aisle.) There was a song change before the B & her dad walked.
I have never been to a wedding that had separate music for the seating of mothers. Traditionally, unless a mother is escorting the bride, there is music for seating guests. And the last to be seated, usually, are grandparents then the parents, and the mothers or mothers with the father or SO escorting mother walking right behind are usually seated to that same music. This is seating. Then, music changes to the processional. .... Traditionally moms are not part of the processional. And in fact, some other people may be seated last minute, from the side aisles, as mothers are seated. It is simply an honor to be escorted to a seat.