can not use old Apple ID without email

I was an early adopter of iOS and originally I had an apple account with just a username and no email.All of the songs I purchased under my original name only id are not accessible on my iTunes account because iTunes does no longer recognizes user id s without an email username.there should be a way to merge user names with email address accounts.Itunes recognizes the username but when my password is entered it states that the account does not exist.

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