Q: How to fix a broken? song

Assuming you are in a region where you are allowed to redownload your past music purchases, delete the broken tracks from your iTunes library (but do not hide from iCloud), close and then reopen iTunes, go to the iTunes Store home page, click the Purchased link from the Quick Links section in the right-hand column, then select Music and Not on this computer. You should find download links for your tracks there.

While downloading click the small download activity widget near the search box and make sure Allow Simultaneous Downloads is unticked. This may improve the reliability of subsequent downloads.

If the problem persists, or that facility is not yet available in your region, contact the iTunes Store support staff through the "Report a problem" links in your account history, or via Contact Support.

See also:

HT5085: iTunes in the Cloud and iTunes Match Availability

HT2519: Downloading past purchases from the App Store, iBookstore, and iTunes Store

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