Q: Transfer music from computer to Ipod with out wiping out excisting music on iPod

Hi there lonsboda, 

Welcome to Apple Support Communities. 

It sounds like you have music on an iPod classic and you want to know how to add music to the device from multiple iTunes libraries. You can add music from multiple iTunes libraries by manually managing the music on the device as shown in the article below.

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

If you're using an iPad or iPod, you can add music from multiple iTunes Libraries, but video from only one iTunes Library.

Take care.

You're welcome.