Hey Agosto Mortal,
Thanks for the update. Just to verify, you want to be within the Music app on the iOS device and put a specific song onto the iMac desktop wirelessly? You can also share the individual song within the Music app using AirDrop to the iMac.
"Learn about other ways you can share files between your Mac and your devices. These features work wirelessly.
iCloud Drive lets you securely access all of your documents from your iPhone, iPad, iPod touch, Mac, or PC. No matter which device you're using, you'll always have the most up-to-date documents when and where you need them.
With Handoff, you can start a document, email, or message on one device and pick up where you left off on another device. Handoff works with Apple apps such as Mail, Safari, Maps, Messages, Reminders, Calendar, Contacts, Pages, Numbers, and Keynote. It also works with some third-party apps.
AirDrop lets you instantly share your photos, videos, documents, and more with other Apple devices that are nearby."
Use the Finder to share files between your Mac and your iPhone, iPad, iPod touch
Have a good one.