Your track probably got corrupted during the download. Delete it, and redownload from the cloud.
Downloading past purchases from the App Store, iBookstore, and iTunes Store
Thanks, that did the trick. I don't pretend to understand Apple's Cloud (it's worked in the past). I was finding the album and track among my recent purchases, but since it showed a faded "downloaded" to the right of it, there appeared to be nothing left to do but highlight, click on the Update Match service, and wait for something good to happen.
"Delete" was the answer. It seemed counter-intuitive, but the instant I trashed it, I had the full track that I was looking for.
I now see that Apple had the album showing twice in order to list it under a 2nd musician.