Under normal market conditions, the Fund seeks to achieve its investment objectives by investing at least 80 percent of its net assets (including investment borrowings) in municipal debt securities that pay interest that is exempt from regular federal income taxes (collectively, Municipal Securities). Municipal Securities are generally issued by or on behalf of states, territories or possessions of the U.S. and the District of Columbia and their political subdivisions, agencies, authorities and other instrumentalities. The types of Municipal Securities in which the Fund may invest as a part of its principal investment strategy include municipal general obligation bonds, municipal revenue bonds, and private activity bonds (including without limitation industrial development bonds). The Fund may invest in Municipal Securities of any duration and any maturity. Interest on private activity bonds may be subject to the federal alternative minimum tax on individuals. For tax years beginning after December 31, 2022, interest on the bonds may affect the corporate alternative minimum tax for certain corporations.