Question#1: I purchased a Macbook and want to know if I download my music from my iPhone 4s to my MacBook, will it delete all songs of my iPhone and be upgraded with the one song I have on the MacBook, since my iPhone isn't synced with this MacBook?
Answer: First, I should say that you can't download music from your iPhone 4s to your macbook unless you authorize your computer with the Apple ID you've used to buy songs on your iPhone in iTunes. Then disable the auto sync in iTunes preferences for devices. Later, transfer purchased songs from your iPhone to your MacBook. To transfer non iTunes purchased songs, refer to -how to transfer all songs from iPhone to Mac. And for sure, if you only transfer purchased songs from your iPhone to Mac without syncing, songs on your iPhone will not be erased.
Question#2: I have two Mac, an iMac and MacBook. I just can't keep my iPhone synced with both the two Mac. It's going to erase my iPhone. Is there any way for me to add songs to iPhone from any of the Mac without iTunes?
Answer: This is how iPhone is designed. To transfer songs from Mac to iPhone via iTunes, you should compare your iPhone with the Mac. If you want to add songs to iPhone on Mac without iTunes, learn how to import songs from Mac to iPhone without iTunes.
Question#3: All my music was purchased onto my iPhone, I don't have an original computer.... Is there some way i can copy it off my iphone or do I have to download all music again through MacBook as the phone and MacBook are using the same iCloud service.
Answer: For this situation, users don't need to download all music again through MacBook but transfer purchased songs from iPhone to Mac via iTunes.
Question#4: How do I sync my iPhone to a new computer without having to erase and sync? I have an iPhone 4s that I have used to sync with my old windows computer. I now have a macbook aird and obiviously I want to start syning my iPhone on my Mac instead of the Windows PC. I want to use Mac iTunes for syncing and putting music from Mac to iPhone, but I don't want to loose any of the music.
Answer: Here are the two solutions: syncing music from Mac iTunes to iPhone and erading the original data or transferring music from Mac to iPhone without iTunes. That's the simplest answer.