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You can buy a ringtone from Apple.

You can also make a ringtone and add to iTunes.

One easy way to do this is to change a songs start and end times to select the part you want, right click, and select "Convert to AAC". That'll add a new track to your iTunes - drag it to your desktop, rename the extension from .m4a to .m4r, and add back to iTunes.
 
great, i just wanted confirmation that the method still worked.
 
The garage band method works too if you have a Mac. Drag file into garage band, trim it, export to itunes as ringtone (its actually int he export menu).

Google it, very easy to do.
 
okay i'm new to iphone... tell me if this is right:
if i want to use different songs in my iphone's 'ipod' for different contacts, i have to put a copy of each song in the ringtones directory?
 
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