The first developer seed of iTunes 10.5.1 implements a new form of manual song sync, notes 9to5Mac. In order to sync individual tracks in v10.5 a person has to rely on iTunes' cumbersome checkbox system, which isn't used for filtering tracks by default, and can affect other sync methods when it is on. The v10.5.1 beta introduces a "Manually Added Songs" section to a device's Music tab, which indicates that people can drag tracks from their Library straight to a device.
