how do I switch an old iTunes email that is no longer in use to recover my music and switched to my new iTunes email?

I take it you mean that you had a different Apple account that you purchased your music from, and then set up a new Apple account?

Whether the email is active or not does not affect the Apple ID itself, so the Apple ID is still out there and functional. However, the only way you are going to be able to get that media onto your device would be to sign that Apple ID into the iTunes & App Store your device and download it. This will result in the device being locked to that other Apple ID for 90 days. You can still sign the other ID back into the iTunes & App Store, but you won't be able to do any of the following on your device under that new ID for 90 days:

Download Past Purchases

Use the Automatic Download feature

Use Apple Music or iTunes Match

Use Family Sharing

Another solution, however, would be to set up Family Sharing with the current Apple ID signed into your device as the Organizer, and then you would invite your old Apple ID to join Family Sharing. Once you had enrolled your old ID, you would have access to that music:

Set up Family Sharing - Apple Support

Apple - iCloud - Family Sharing

That way you would avoid the 90-day Associated device situation.

Best of luck,

GB

Wat

Do you have a question?

GB