oh...! I understand.
you need to make the same change on line 173 which is for the infividual song page. the other was for album page.

no. this is checked on a specific song page

it should work.. are you checking this on the Album page?

I've done this but it did not work

if you open file /plugins/muscolplayers/jwplayer.php and you go around line 136, you will see "autostart:false"
you need to set it to "autostart:true"

can you direct me what modification l'll need to do and on which file?

you would need to make a small code modification on the player's file to allow that.