Q: How do I remove music from an old iPod (nano?)

Hi Footplate,

Thank you for using the Apple Support Communities. 

If you are looking for more information on manually deleting content from an iPod nano via iTunes, you may find the following discussion helpful (apologies if this is one of the answers you have already looked at):

how to delete songs from my ipod | Apple Support Communities

If the delete function is not behaving in the way described in that thread, you may need to restore your iPod to factory settings, then sync your content back to your iPod from iTunes. Note that this will remove all content from the iPod, including any that was synced from another computer or outside your current iTunes library:

Move content from iTunes on your computer to your iPhone, iPad, or iPod touch - Apple Support

Use iTunes to restore your iPhone, iPad, or iPod to factory settings - Apple Support

Sync your iPhone, iPad, and iPod with iTunes using USB - Apple Support

Regards