UPDATE, with production dates : Imitation of Life , the new musical with a book by Lynn Nottage , music and lyrics by John Legend , and direction by Liesl Tommy will begin performances on Wednesday, September 9, at The Griffin Theater at The Shed Off Broadway . A co-production of The Shed and National Black Theatre, Imitation of Life will play a strictly limited four- week presentation engagement through Sunday, October 4. In the announcement today, the production was described as The Shed’s “first major step in nurturing and developing a new American musical. The musical will be performed with full cast and live orchestra. Additional details including casting, design and creative team members will be announced at a later date.…