Q: Transferring music from MAC PRO to an iPhone?

By putting the music into an iTunes Library (see iTunes Help) then syncing to the iPhone: (Please get iPhone User Guide for iOS 8.1.)

Sync your iPhone, iPad and iPod touch with iTunes using Wi-Fi

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

Connect your iPhone to the Mac, open iTunes, select the phone from the bar above. Go to Music and select the songs or albums you want to sync. Then just do a sync and your selected music will appear on your phone.

I just found one of the software I used. It's called, "iTools". And it's free for transferring music from Mac Pro to iPhone. I just transferred an album of music to the iPhone with it. The problem is, the mp3 tag information did not transfer along with. So the artist names do not show, and the songs don't get properly categorized. If this exists, there must be something better out there that will transfer both the songs and their id3 tags from Mac to iPhone.

Yes there is, it is called iTunes. Click on the links Kappy provided to learn how to do so.