The fund seeks a high level of current income exempt from federal income tax. The fund invests at least 50% of its assets in investment-grade municipal securities or unrated municipal securities of comparable quality, and may invest up to 50% of its assets in high-yield municipal securities that are below investment grade. Closed-end funds, unlike open-end funds, are not continuously offered. There is a one time public offering and once issued, shares of closed-end funds are sold in the open market through a stock exchange. Shares of closed-end funds frequently trade at a discount to net asset value. The price of the fund’s shares is determined by a number of factors, several of which are beyond the control of the fund. Therefore, the fund cannot predict whether its shares will trade at, below or above net asset value. Bond investments are subject to interest-rate, credit, liquidity and market risks to varying degrees. When interest rates rise, bond prices generally fall. Credit risk refers to the ability of an issuer to make timely payments of principal and interest. Municipal securities are subject to the risk that litigation, legislation or other political events, local business or economic conditions or the bankruptcy of the issuer could have a significant effect on an issuer’s ability to make payments of principal and/or interest. The market for municipal bonds may be less liquid than for taxable bonds and there may be less information available on the financial condition of issuers of municipal securities than for public corporations.Investing in derivatives entails special risks relating to liquidity, leverage and credit that may reduce returns and/or increase volatility. Leverage results in additional risks and can magnify the effect of any gains or losses. Although the fund seeks income that is exempt from federal income taxes, a portion of the fund’s distributions may be subject to federal, state and local taxes, including the alternative minimum tax. War, terrorism, economic uncertainty, trade disputes, public health crises (including the recent pandemic spread of the novel coronavirus) and related geopolitical events could lead to increased market volatility, disruption to U.S. and world economies and markets and may have significant adverse effects on the fund and its investments.