The fund invests at least 80% of its net assets, plus amounts borrowed for investment purposes, in tax-exempt bonds of any maturity. It primarily invests in bonds that are investment grade when purchased, but the fund may also invest up to 35% of its net assets in non-investment grade bonds rated BB or lower by S&P, Fitch, or Moody’s, or comparable rating by any NRSRO or unrated equivalents. The fund may buy bonds of any maturity or duration.