Janet, I am no expert on Apple products, but my understanding is that older versions of Quick Time can play midi files. Try to install QT 7 and see if that works.
Another (more time consuming) solution would be to use one of the many free online audio converters to convert the midi files to mp3 files. If you put "Free online audio coverter) in the Google search bar, you'll find plenty of options. Don't use any that ask you to register or demand payment.
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Dusty T., Northern California
Site Moderator
As a musician, you have to keep one foot back in the past and one foot forward into the future.
-- Dizzy Gillespie