4:21 ...The Day After is an album produced by man who was the leader of what group? 
4:21... The Day After:  Production is handled by RZA, Havoc, Kwamé, Erick Sermon and Scott Storch, amongst others. RZA:  A prominent figure in hip hop, RZA is the "de facto" leader of the Wu-Tang Clan.
Wu-Tang Clan