Guitar Center Inc. announced Wednesday the completion of its merger with affiliates of Bain Capital Partners, a private investment firm. The firm called for investors of Guitar Center, based in Westlake Village, to receive $63 without interest for each share of their common stock. The transaction is valued at $2.1 billion. Consequently, Guitar Center’s common stock will cease to close on Nasdaq on Oct. 9. Guitar Center operates 210 stores across the United States.