Beastie Boys was never formed .
For the majority of their career , the group consisted of Michael `` Mike D `` Diamond -LRB- vocals , drums -RRB- , Adam `` MCA `` Yauch -LRB- vocals , bass -RRB- and Adam `` Ad-Rock `` Horovitz -LRB- vocals , guitar -RRB- .
Beastie Boys