Posthumous reform

I got an email today telling me this:

On Saturday 26 November 2011, Seaham Harbour's A Woman of No Importance will reform to play a special show at Newcastle Arts Centre, in aid of Macmillan Cancer Support. The band will perform their posthomously released compilation album, 'AWoNI' (fakeindielabel, 2007) in it's entirety, in order.

I'm intrigued as to what tragedy could have wiped out the whole band, but what I really want to know is how a band can possibly reform and perform their posthumously-released compilation album.