Ipod Not Syncing

I have an iPod Classic which syncs to my iMac. It has been doing so for years without issues.

Recently however, i had to wipe my entire iMac and start over with a new copy of the O/S (long story).

In any event, I realized that if I were to try to sync my iPod with a fresh blank copy of Itunes, it would not include music I did not purchase from the app store . As I am a musician, i have a lot of songs that I wrote that are on my iPod.

My music catalogue, including my original songs, are held on a NAS drive. What i did, was that I dragged all the music from my NAS, to my Itunes's library. I then attached the iPod.

I am not sure if it did sync or not. I do know that the process of copying the files from my NAS to iTunes, took a long time.

So here is the problem:

My iPod seems to have a ton of music on it, including my original songs (that's good). However, when I add a new song to iTunes ( a new original song for example), it does not sync.

In Itunes, my iPod also used to have a small icon that i could right click on and click on sync, and it would do so. Now that Sync item is not there.

When I double click on the Iopd Icon and got to it's window in Itunes, I can hit the sync button, and it says "syncing" but the new original songs do not appear.

The funny thing is, that all my old playlists are still on my iPod. I wasn't expecting them to be there. So maybe the initial huge sync did not work and the stuff I am seeing on my Iopd is the old stuff?

I guess my question is, how do i get my iPod back to a place where it has all my music, and that it syncs. I have all my music on my NAS, so it is not a problem accessing it. But how do i get my iPod to function properly with it? I have no problem resetting my iPod and wiping it if need be.

Any help would be greatly appreciated.

Thank-you