Add music without iTunes on iPod Nano

I have a new iPod Nano and I want to put music on it, but I have to upgrade my iTunes, which isn't an option. (have to update OS X on computer too) How would I be able to encode my iTunes songs to be transferred to the internal files (***s iPod > iPod_Control > Music) coz I tried to just send the files as is but it wouldn't load.

Tysm y'all!