Don't really want to delete things but I cannot get OS 8 on phone due to lack of space. Have backed up phone using i tunes to the mac but don't know what to do after that. Can I delete music or photos and get them back easily after the download?? All the sites addressing this are confusing.
Have you tried updating your device through iTunes, instead of directly on the device? Click "check for updates" on your device's page in iTunes. This method needs less free space than updating through your phone.
As long as your music is still on your computer, or you purchased it through iTunes, then yes, it will be easy to restore you music if you need to delete it.
Apple's site it pretty clear and included links to free up space on iOS when you want to perform an OTA update.