Clustering preferences

I have list of people, each of whom has picked 20
musical groups as their favorites. I would like
to find clusters among the musical groups: for example,
if people who enjoy group A also enjoy group B, but don't
enjoy group C, then A and B should be clustered together
and C should be in a different cluster.

I seem to remember some algorithm that would perform this
clustering (collaborative filtering, naive bayes?). 

What algorithm am I looking for?

Thanks,
Salem

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