Why is my iPhone syncing random songs?

So every once in awhile while I'm listening to music on my phone it starts playing some song that is not on any of the playlists i sync to my phone. I've made sure that I didn't accidentally add those songs to the playlists or tell it to sync another playlist, they just randomly show up. Why is this happening?

You have auto-fill selected.

Select the device in iTunes.
Click the Music tab and uncheck Automatically fill free space with songs.

  • Why is there random songs on my iTunes? There's like 11 songs on my iTunes and I don't even know the songs and I don't have money on my account I have an iPhone 5s
  • Why aren't my songs from iTunes syncing to my iPhone? I have 1365 songs in my iTunes library which I can play. But only 1260 songs are transferring over to my iPhone. I just got a replacement iPhone about 4 days ago so I'm not sure if that has to do with anything?
  • Why aren't all my songs syncing onto my iPhone? I just got my iPhone last week, and after I synced all my songs (590 of them) to my computer, I tried to sync them onto my iPhone. However, only 345 of them are syncing. In iTunes the box next to "Sync Music" and "Entire Music Library" is checked. Down at the bottom the bar that shows how much music, apps, photos, etc.shows that I have 590 songs, but once I click "Apply" it syncs, but the bar reduces to only 345 songs!
  • Syncing iPhone songs onto iTunes? Okay so what I want to do is make ringtones on my iPhone 4s. But in order to do that I have to sync my iPhone to iTunes. Which I haven't done yet with my phone. I have 60 songs that i bought on itunes store on my phone but I don't want to lose them. And i heard if I sync my phone to the computer that it will wipe everything out of it? So is there any way to sync the songs and all the apps and media from my phone onto itunes on my laptop?