How to sync music from a different iTunes account to my iPhone?

I remember as a little kid I would always have to use the account on my dads computer to get music on my iPod video. But then when I was eleven I bought an iPod touch and I created a whole new account based around my email, not his. But on my old iPod I had a bunch of great mid-2000s hip hop on it (before it was murdered by soulja boy in 08. Ever since him it pretty much sucks), and I also bought a bunch of kickaśs classic rock from queen to Jimi Hendrix to foghat to stones, etc. When I was 10. But how do I sync the songs on my dads iTunes to my iPhone 4 of a different account

How to Sync an iPhone to Two iTunes Accounts

Instructions

1

Back up the data from the second computer that the iPhone is being synced to. This will eliminate accidental deletion of iTunes media on the second computer.
2

Select and download a hex editor. This is a program necessary for syncing the iPhone to two iTunes on separate computers.
3

Open "iTunes Music Library.xml" on the original computer. Open it in Notepad or a similar software and press "CTRL" and "F" to bring up find features. Type in "<key>Library Persistent ID<key>" and look for the code between the two "<string>" commands that follow immediately after the "Library Persistent ID."
4

Locate the code on the second computer. Replace the code between the two "<string>" commands on the second computer with the code from the first computer. Open the iTunes Library on the second computer and start the hex editor and select "Edit." Type in the code for the second computer in "Find" and then type the code from the first computer in "Replace With" and select "Replace." This will replace all of the codes throughout the iTunes on the second computer. Save the file when the hex editor completes.
5

Plug the iPhone into the second computer via the USB cord and select "Manually Manage Music and Videos."