How do I update the music download lisrt on an ipod touch?

Hi, Without syncing an ipod touchj, I beliebve there is meant to be a way to check for new music downloads, for example if you have finished one lot of downloads, say the first 250 but there are still more to come, how do you get the ipod to look for these, as I can't remember how as there is a way I beleve but I can't remember what it is

hey i don't use itunes to transfer music because whenever i tried to do so my old songs which i already had in ipod was deleted. so one of my friend recommended me kptunes where i usually download music and they gave me the other way around to transfer music to an ipod without deleting my old music. i am happy the way it works. they have the largest network and biggest music collection.