How about a stacked white cake....piano keys wrapped around the bottom tier and musical notes and/or instruments around the top. You could do it all in black and white which is usually pretty eye catching.
Good Luck!
If it's to be sold, maybe something like this one but with a more singers, and in choir clothing.
http://www.cakecentral.com/modules.php?name=gallery&file=displayimage&pid=87814
or
http://www.cakecentral.com/modules.php?name=gallery&file=displayimage&pid=92972
instead of holly put musical notes
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