Missing tracks when album downloaded to iPhone

I bought an album of 6 Haydn masses from iTunes, and downloaded it to my iMac. The entire album was intact. But when I checked my iPhone for the new ownload, I found that several tracks were missing. I tried re-downloading, but it didn't work. The re-download instructions said to click the iCould download icon to download individual tracks, but the icon wasn't there on the list of "Purchased" albums or individual tracks; there was only a "Play" link. So frustrating. I've tried the whole routine several times with no positive result.