iMac won't play music discs

Don't understand, wasn't a problem before. It will recognise all other discs and allow access but when I put a music CD in, it makes a sound like it is checking it out and then it spits it out. Have I done something weird?

Have you tried it with multiple disks, or just one? Might be a bad disk.

Thank you for the response. Yes, I tried it with multiple disks. I knew something was BIZARRE when it wouldn't play any music at all except Bob Marley. So I fell back on an old PC trick. I rebooted. I have to say I have only had to reboot my iMac every blue moon compared to my PC; whatever, it worked. Thank goodness. I am okay with Bob Marley but hardly wanting that to be my sole musical fare!