Ghost note (of Motown), Rocco Prestia (for Tower of Power), and Chuck Rainey (for Steely Dan, Aretha Franklin, and others) all include "tons of ghost notes done right" in their playing. In vocal music, especially in musical theater, a ghost note represents that the lyrics must be spoken rather than sung, retaining the marked rhythm but having indeterminate pitch. Notes with value less than a half note use an "X" instead of an oval as a note head. Occasionally a half note or whole note is represented with an open diamond note head, often representing a scream or grunt. As an extreme
Time value of money not already occurred), or simply not define the value at that point. In case the discount rate is constant, formula_47 this simplifies to where formula_49 is "time remaining until cash flow". Thus for a stream of cash flows "f"("u") ending by time "T" (which can be set to formula_50 for no time horizon) the value at time "t," formula_51 is given by combining the values of these individual cash flows: This formalizes time value of money to future values of cash flows with varying discount rates, and is the basis of many formulas in financial mathematics, such as the Black–Scholes