How to remove/reset mp3 from ipod? I'm trying to remove some artists from the iPod, but it's not working. I can remove in the iTunes, and sync, but when I look in the iPod, they are still there.

The iTunes show more "empty space" in the graph, but in the iPod there's almost no free space.

I've tried to remove all mp3 and synchronize, but after the process I look in the iPod and the mp3 are still there.

Is there a way to remove the mp3 without need to format the iPod?

(I don't want to loose some applications saved data, and I'm not sure if iTunes would correctly bkp my saved games achievements, for example)
Go to settings, general, usage, music, swipe across all music and tap delete. If that doesn't work, try restoring it in iTunes. Plug it in and turn your iPod off, then hold the power and home buttons for eight seconds(a little bit after the screen turns black again) then release the power button but hold the home button for about seven seconds, or until iTunes recognizes it and tells you to restore it. After it is restored you will be able to restore your save data with iCloud if your device runs ios 5.If it doesn't, wait for another answer.