Hi , Yes you do not need to migrate your old user account if you just want a new user account .
You just need to authorize your itunes account on the new Mac , and de-authorize it on the old Mac , more below.
You can setup itunes sharing between the two Macs to make sense of this and how to move your itunes library . . Once completed de-authorize remove the old Mac from sharing .
Please read all the below , and understand how to move files around and share files in itunes or from the desktop . If you need extra help please ask I can guide you though .
See sharing section lower down to share you music library across your computers and ipod / iphone etc .
There are a number of ways to use extra media drives and computers with itunes .Please turn off the option to copy files to the itunes library as below.
Adding items to your library without copying them to your iTunes folder.
When you import a song from a CD or download a song from the Internet, the song file is placed here:
[Home]/Music/iTunes : default .
When you add an item to your library by dragging it to the iTunes window or choosing File > Add to Library, iTunes places a copy of the file in your iTunes folder; the original file remains in its current location.
You can change this setting so that the item appears in iTunes without being added to the iTunes folder. You might want to do this so that, for example, you could save video files in a location other than your hard disk.To add files to your library without adding them to your iTunes folder:
Choose iTunes > Preferences and click Advanced.
Deselect the “Copy files” checkbox.
You can now drag an entire "other" music folder to the itunes music library window , the files will be added to the library but not copied from there location.
If in future you purchase a External HD large enough for all media in your itunes library / playlists etc , you can use the consolidate library option to copy all itunes library content to the new location set in the itunes preferences for itunes media folder location. After that consolidation you may delete the old music files in the old locations used. Please check all content is copied to the new location before hand to make sure before removal of the old files ..
Other options :
To create or use a different iTunes library:
If iTunes is open, quit it.
Hold down the Option key while you open iTunes.
In the dialog that appears, do one of the following:
To create a new library, click Create Library.
To choose a different library, click Choose Library.
-Sharing options :
Things may change as itunes moves cloud based. . "online streaming , downloads " etc , this may make sharing even more flexible.
Ipod sync is one way in most cases , although. Sharing :
In itunes try using the File menu and transfer purchases from ipod , to the second Mac or PC .
You my need to Authorize the computer to share your music and downloads at which point you will be asked for your apple ID and password XXXXX
Purchases on the ipod will be copied to itunes .
Sync the ipod so all music and data is current.
If you have music from a different computer , make sure it is shared with the second computer using home sharing . Once the music and data is shared across all computers and ipod / iphone , then you can remove the computer that is not being used anymore . See Deauthorize computer in the Store menu , and turn off sharing for this computer as below. More on home sharing:
There is a home sharing option built in to itunes 9 onward .
You can use this to share the music in the home place network .
-Sharing your iTunes library across computers
If your computer is connected to other computers over a local network, you can share items in your library with up to five of those computers.
While your computer is on and iTunes is open, others in your network can play your shared items, but shared items can’t be imported into others’ libraries.
If you want to import items from other iTunes libraries on other computers in your home, you can turn on Home Sharing.
You can use Home Sharing with up to five computers.
To use Home Sharing, you must have an iTunes Store account.
Sharing is intended for personal use only.To share your library with other computers on your local network:
Choose iTunes > Preferences, click Sharing, and select “Share my library on my local network.”
Select the items you want to share.
To require users to enter a password XXXXX they can see your shared items, select “Require password” and enter a password.
If you choose to share your entire library, its name appears in the iTunes window (below Shared) on other local computers set up to look for shared libraries.
To change the name others see, choose iTunes > Preferences, click General, and type a new name in the Library Name field.
-To turn off sharing:
Choose iTunes > Preferences and then click Sharing.
Deselect “Share my library on my local network.”
To import items from other libraries using Home Sharing:
Choose Advanced > Turn On Home Sharing.
Type your iTunes account name and password, and then click Create Home Share.
Using the same user name and password, repeat steps 1 and 2 on each computer.
To import items from another computer, select the computer (below Shared), and drag items from its library to yours.
To automatically import iTunes Store items that are downloaded to a computer you’re Home Sharing with, select “Automatically import new purchases from [Computer Name].”
-To turn off Home Sharing:
On each computer, choose Advanced > Turn Off Home Sharing.
You can share movies; radio station links; and MP3, Apple Lossless, AIFF, WAV, and AAC files. You can’t share programs purchased from Audible.com or QuickTime sound files.
You can also find this info in Itunes help , launch itunes , use the top screen help menu , select itunes help , search for home sharing.
-Alternative solution .
Note : Apple TV is the easiest way to share music , video and pictures etc on the local home network .
It basically is a HDD networked box that plugs in to the home HD TV and audio center . Apple TV connects to a local network via Wifi and serves music and film wireless to all computers on the network or directly to the HD TV plugged in to it .
http://store.apple.com/uk/browse/home/shop_ipod/family/apple_tv?afid=p202|GOUKE100819837&cid=OAS-EMEA-KWG-UK_TV-UKOnce you are shared across all you computers and authorized , and Deauthorized if needed "if a computer is not used any more or to be sold" ..
If you have music on a second PC that is imported via audio CDs or downloads or your own music etc and you don't want to authorize the other computer .
Just burn an MP3 CD/s and copy the music to the itunes folder by adding the music to the itunes library , check import settings in itunes preferences .
Be aware of copyright on music and other MP3 or video content.
I hope this helps .