Keep in mind that municipal securities are subject to a number of risks including, but not limited to: Interest Rate Risk, the risk that the market value of fixed-income securities may fluctuate when interest rates change, and Prepayment Risk, the risk that the issuers of individual securities may prepay them at a time when interest rates have declined.

FORBES: Put Intermediate Muni Funds In Your Portfolio's Rotation

The fact that early bonds had no fixed maturity date ensured that any change in interest rate was fully reflected in the capital value of the bond.

ECONOMIST: What did early 19th-century literary characters live on?

Whereas an old-style trust pays out only investment income (dividends and interest) to "income" beneficiaries, a TRU pays them a fixed percentage of its value annually--typically 3% to 5%.

FORBES: New Cash From Old Trusts