CD with multiple artists downloads into iTunes as a separate album for each artist

I recently began having a problem when I added an audio CD to iTunes (downloaded from the CD drive). The CD was of an album by one artist, but a second artist joined him on track 1. iTunes downloaded this as two separate albums; one with tracks 2- 10 and the other with track 1. This hadn't happened before. I can't find a control concerning this. Thanks.