Link slider to track progress? Multiple midi players?

Hey, I have a couple questions

First I was wondering if it is possible to link a slider bar to the track progress of a song.

Second is that I’m working on a project that has multiple (homemade) midi players in one animation, and I wasn’t sure how I would go about making each one able to play a song whenever clicked on – at the moment my problem is with the slider bars (wich are now linked to the volume) – Whenever I change one’s position, I guess it sets itself as the only volume bar, and when I move the others it doesn’t make a difference - I’m kindof confused how it works.

Thanks for the help, you guys are great :A+:
-wyatt