be.tarsos.dsp.util

Class PitchConverter

java.lang.Object

be.tarsos.dsp.util.PitchConverter

public final class PitchConverter
extends java.lang.Object

Converts pitch from one unit to another (and back (and back (and back ...))).

Author:

Joren Six

Method Summary

Methods

Modifier and Type	Method and Description
static double	absoluteCentToHertz(double absoluteCent) Returns the frequency (Hz) of an absolute cent value.
static double	centToRatio(double cent) Converts cent values to ratios.
static double	hertzToAbsoluteCent(double hertzValue) The reference frequency is configured.
static double	hertzToMidiCent(double hertzValue) Converts a frequency in Hz to a MIDI CENT value using (12 * log2 (f / 440)) + 69 E.g. 69.168 MIDI CENTS = MIDI NOTE 69 + 16,8 cents 69.168 MIDI CENTS = 440Hz + x Hz
static int	hertzToMidiKey(java.lang.Double hertzValue) A MIDI key is an integer between 0 and 127, inclusive.
static double	hertzToRelativeCent(double hertzValue) Converts a Hertz value to relative cents.
static double	midiCentToHertz(double midiCent) Converts a MIDI CENT frequency to a frequency in Hz.
static double	midiKeyToHertz(int midiKey) Calculates the frequency (Hz) for a MIDI key.
static double	ratioToCent(double ratio) Converts a ratio to cents.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

hertzToMidiKey

public static int hertzToMidiKey(java.lang.Double hertzValue)

A MIDI key is an integer between 0 and 127, inclusive. Within a certain range every pitch is mapped to a MIDI key. If a value outside the range is given an IllegalArugmentException is thrown.

Parameters:

hertzValue - The pitch in Hertz.

Returns:

An integer representing the closest midi key.

Throws:

java.lang.IllegalArgumentException - if the hertzValue does not fall within the range of valid MIDI key frequencies.

midiKeyToHertz

public static double midiKeyToHertz(int midiKey)

Calculates the frequency (Hz) for a MIDI key.

Parameters:

midiKey - The MIDI key. A MIDI key is an integer between 0 and 127, inclusive.

Returns:

A frequency in Hz corresponding to the MIDI key.

Throws:

java.lang.IllegalArgumentException - If midiKey is not in the valid range between 0 and 127, inclusive.

hertzToRelativeCent

public static double hertzToRelativeCent(double hertzValue)

Converts a Hertz value to relative cents. E.g. 440Hz is converted to 900 if the reference is a C.

Parameters:

hertzValue - A value in hertz.

Returns:

A value in relative cents.

hertzToAbsoluteCent

public static double hertzToAbsoluteCent(double hertzValue)

The reference frequency is configured. The default reference frequency is 16.35Hz. This is C0 on a piano keyboard with A4 tuned to 440 Hz. This means that 0 cents is C0; 1200 is C1; 2400 is C2; ... also -1200 cents is C-1

Parameters:

hertzValue - The pitch in Hertz.

Returns:

The value in absolute cents using the configured reference frequency

absoluteCentToHertz

public static double absoluteCentToHertz(double absoluteCent)

Returns the frequency (Hz) of an absolute cent value. This calculation uses a configured reference frequency.

Parameters:

absoluteCent - The pitch in absolute cent.

Returns:

A pitch in Hz.

hertzToMidiCent

public static double hertzToMidiCent(double hertzValue)

Converts a frequency in Hz to a MIDI CENT value using (12 * log2 (f / 440)) + 69
E.g.
69.168 MIDI CENTS = MIDI NOTE 69 + 16,8 cents
69.168 MIDI CENTS = 440Hz + x Hz

Parameters:

hertzValue - The pitch in Hertz.

Returns:

The pitch in MIDI cent.

midiCentToHertz

public static double midiCentToHertz(double midiCent)

Converts a MIDI CENT frequency to a frequency in Hz.

Parameters:

midiCent - The pitch in MIDI CENT.

Returns:

The pitch in Hertz.

centToRatio

public static double centToRatio(double cent)

Converts cent values to ratios. See "Ratios Make Cents: Conversions from ratios to cents and back again" in the book "Tuning Timbre Spectrum Scale" William A. Sethares.

Parameters:

cent - A cent value

Returns:

A ratio containing the same information.

ratioToCent

public static double ratioToCent(double ratio)

Converts a ratio to cents. "Ratios Make Cents: Conversions from ratios to cents and back again" in the book "Tuning Timbre Spectrum Scale" William A. Sethares

Parameters:

ratio - A cent value

Returns:

A ratio containing the same information.