How to get songs from my computer to iPhone 4S without iTunes?

I want to get songs from my laptop to my iPhone without using iTunes but I'm not sure how.

I don't want to use iTunes on my laptop because every time I do it messes up my songs, deletes ones that are from my account and causes the songs on my phone to skip constantly. However the songs I want to get on my phone show up on iTunes on my laptop even though they are not available on iTunes (I got them from the artist's site from soundcloud).

Is there any way I can do this without using iTunes? I can see the album and listen to the songs and everything from iTunes on my laptop and the album is also saved to my laptop. I would buy the songs if they were on iTunes but they aren't on there, only on the artist's site for free.

Try Diskaid.