The investment seeks to provide a high current yield exempt from federal income tax. The fund normally invests at least 80% of assets in municipal securities whose interest is exempt from federal income tax. The fund invests primarily in investment-grade municipal securities. The fund allocates assets across different market sectors and maturities. The fund potentially invests more than 25% of total assets in municipal securities that finance similar types of projects. The fund invests up to 30% in lower-quality debt securities (those of less than investment-grade quality, also referred to as high yield debt securities or junk bonds).