`#include "MusimatTutorial.h"`

Go to the source code of this file.

## Functions | |

MusimatTutorialSection (B0201a) | |

Real | pitchToHz (Pitch p) |

Void | para1 () |

Pitch | hzToPitch (Real x) |

Void | para2 () |

Pitch hzToPitch | ( | Real | x ) |

Definition at line 51 of file B0201a.cpp.

References pitchToHz().

{ // find pitch closest to x Hz For(Integer k = 9+1; k < 88+9; k = k + 1) { // test from As0 to C8 Pitch p = Pitch(k); // get pitch of k Real f = pitchToHz(p); // get frequency of p If (f > x) // have we passed our target? Return(p - 1); // return previous pitch } // If we get here, the Hz value of x is beyond the end of the keyboard Return(C8); // out of range, clip at C8 }

MusimatTutorialSection | ( | B0201a | ) |

Definition at line 2 of file B0201a.cpp.

References para1(), and para2().

{ Print("*** Equal-Tempered Frequency ***"); /***************************************************************************** Equal-Tempered Frequency Pitch provides a representation of scale degrees and does not denote frequency. We can convert to frequency using any scale system we like, beginning with the equal-tempered scale. We can compute the equal-tempered frequency of a Pitch, assuming a reference such as A4 equals 440 Hz, by adapting equation (3.3), f(k, v) = fR * 2^(v + k / 12), to compute hertz values from chromatic scale degrees: *****************************************************************************/ para1(); // Step into this function to continue the tutorial para2(); // Step into this function to continue the tutorial }

Void para1 | ( | ) |

Definition at line 27 of file B0201a.cpp.

References pitchToHz().

{ /***************************************************************************** A way to think about the expression in the Return() statement is as follows. Suppose the reference pitch is 440 Hz, corresponding to A4. So we want the value returned from this function to equal 440.0 when p is A4. The triple for A4 is (9, 0, 4), so when pitchToHz() is called with A4, we want to evaluate fR * 2^0, which can be achieved by subtracting 9 from the pitch and 4 from the octave. Then, executing *****************************************************************************/ Print(pitchToHz(A4)); /***************************************************************************** prints 440.0, and substituting any other pitch, regardless of how it is spelled, will produce its proper hertz value. For example, A0 is 27.5 Hz, C4 is 261.63 Hz, and C8 is 4186.01 Hz. What if we have a frequency x in hertz and want to find its corresponding pitch? The problem is that x may lie in between the pitches of the scale because x can be any frequency. One approach is to compare x to each semitone on the keyboard from lowest frequency to highest, and to stop when the keyboard frequency exceeds x. Then the key one semitone below is the closest corre- sponding pitch on the keyboard. *****************************************************************************/ }

Void para2 | ( | ) |

Definition at line 62 of file B0201a.cpp.

{ /***************************************************************************** This code returns A0 if x is lower than or equal to A0, and it returns C8 if x is greater than or equal to C8. Lists of Pitches We can collect pitches into lists: *****************************************************************************/ PitchList shave(C5, G4, G4, Ab4, G4, B4, C5); // shave and a haircut, 2 bits /***************************************************************************** We can do arithmetic on all the pitches in a list. To transpose this pitch list up a whole step, *****************************************************************************/ Print( shave = shave + 2 ); /***************************************************************************** adds two degrees to every pitch in shave, and prints {D5, A4, A4, As4, A4, Cs5, D5}. To transpose by an octave, *****************************************************************************/ Print( shave = shave * 2 ); /***************************************************************************** multiplies every pitch in the list by 2 and prints {D6, A5, A5, As5, A5, Cs6, D6}. *****************************************************************************/ }

Real pitchToHz | ( | Pitch | p ) |

Generated on Fri Nov 26 2010 16:18:26 for Musimat Tutorial by 1.7.2