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SOUNDSHAPER: CDP REFERENCE

TRANSPOSE - pitch shift with optional formant preservation


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SPECTRAL
FREQ/PITCH
repitch transpose(f)
pitch transp / octmove

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SUMMARY
Transpose sound up or down in pitch, optionally preserving the spectral envelope. The time-base (i.e. speed/rhythm) is preserved in each case.

TRANSPOSE: straight transposition with options for preserving spectral envelope
TRANSPOSE_TRN: Variant of TRANSPOSE using binary transposition file
SHIFTPITCH: transpose all or part of spectrum
OCTMOVE: transpose using pitch data file,
preserving spectral envelope
TRANSPOSE
Pitch-shift the whole spectrum, preserving time and optionally the spectral envelope.
Several ways of entering the transposition are offered: by frequency ratio, octaves or semitones. There is also an option to filter out part of the spectrum. 

In the "straight transposition" modes (1,4,7), the spectral envelope is also shifted.
In the other modes (2/3, 5/6, 8/9) the spectral envelope is preserved
; unfortunately these modes mostly seem to produce unwanted artefacts.

MODES
 1.   Freq.ratio: transpose by frequency ratio
 2/3.Freq.ratio with formants: transpose by frequency ratio preserving spectral envelope; formants extracted by freq (Mode 2) /pitch (Mode 3).
 4.   Octaves: transpose by number of octaves
 5/6.Octaves with formants: transpose by octaves preserving spectral envelope; formants extracted by freq. (Mode 5) /pitch (Mode 6).
 7.   Semitones: transpose by number of semitones
 8/9 Semitones with formants: transpose by semitones preserving
spectral envelope; formants extracted by freq. (Mode 8) /pitch (Mode 9).

OPTION
• Fuller spectrum:  a more detailed spectrum is used.

PARAMETERS

 ratio: Frequency ratio (Modes 1-3), e.g. 2=+8ve, 0.5=-8ve
Range: 0.00383 to 256  T-V
 octaves: Number of (possibly fractional) octaves (Modes 4-6).
Range: -8.0 to +8.0  T-V
 transposn: Number of (possibly fractional) semitones (Modes 7-9).
Range: -96.0 to +96.0  T-V
 [low freq]: FILTER OPTION: filter out all frequencies lower than this.
Range: 5-22050 Hz.  T-V
 [high freq]: FILTER OPTION: filter out all frequencies lower than this.
Range: 5-22050 Hz.  T-V
 channels - Mode 1:  No. of frequency channels per point used to extract spectral contour (fewer more accurate)
Range: 1-100
 bands - Mode 2: No. of pitch bands per octave used to extract spectral contour (greater more accurate)
Range:  1-12


TRANSPOSE-TRN
Pitch-shift the whole spectrum using a binary transposition file, optionally preserving spectral envelope.
CDP Transposition files are created by combining Pitch Data files (.frq) and/or other Transposition files. The transposition data must have come from sounds of definite pitch. See PITCH section for further details.

MODES
 1.   Transpose: transpose whole spectrum using transposition file 
 2/3.Transpose preserving formants: transpose by transposition file preserving spectral envelope; formants extracted by freq (Mode 2) /pitch (Mode 3).

OPTION
• Fuller spectrum:  a more detailed spectrum is used.

PARAMETERS

 [low freq]: FILTER OPTION: filter out all frequencies lower than this.
Range: 5-22050 Hz.  T-V
 [high freq]: FILTER OPTION: filter out all frequencies lower than this.
Range: 5-22050 Hz.  T-V
 channels - Mode 1:  No. of frequency channels per point used to extract spectral contour (fewer more accurate)
Range: 1-100
 bands - Mode 2: No. of pitch bands per octave used to extract spectral contour (greater more accurate)
Range:  1-12


PITCH SHIFT
Transpose part of the spectrum, preserving time but not spectral envelope.
Though the function is designed to transpose a given frequency range, this can in fact be the whole spectrum.


MODES
 1. Octave up:  Partials above freq split are transposed up an octave. 
 2. Octave down:  Partials below freq split are transposed down an octave
 3. Octave up+down:  Partials above freq split are transposed up an octave; those below it down an octave. 
 4. Pitch up: Partials above freq split are transposed up by transposn semitones.
 5. Pitch down: Partials below freq split are transposed down by transposn semitones.
 6. Pitch up+down: Partials above freq split are transposed up by transposn semitones; those below it by transp down semitones.

PARAMETERS
 freq split
: shift above/below this frequency.
Range: 5-22050 Hz.  T-V
 transposn: Number of (possibly fractional) semitones to shift up (in Modes 4+6) or down (in Mode 5).
Range: -96.0 to +96.0  T-V
 transp down: Number of (possibly fractional) semitones to shift down (in Mode 6).
Range: -96.0 to +96.0  T-V
 [depth]:  Depth of effect - degree to which  source partials are replaced
Range: 0-1 (0 - no replacement, 1 - full replacement)  T-V


OCTMOVE
'Octave' transposition preserving formants
This function needs a second Infile: a binary pitch file derived from the source. In Soundshaper, just click on the input cell when the red panel 'Input 2nd-file' appears, and the pitch file will be created automatically (unless there is no definite pitch to trace). Use only with monophonic sounds of definite (possibly changing) pitch.

Despite the title, other ratios such as 3 (12th) also work.


MODES
 1. Up:  Transpose up
 2. Down: Transpose down

 3. Down with bass boost (or gain reduction)

PARAMETERS
 
transpos'n: Transposition expressed as multiple (Mode 1) / ratio (Modes 2/3): 2 is 8ve, 3 is 12th, 4 is two 8ves, etc.
Range: 2 to 4096 Whole-numbered values only: fractional values are ignored.
 bass boost: Boost or reduce gain.
Range: 0 -1-50 T-V


NOTES
TRANSPOSE is a workhorse function for changing pitch without changing time. With most sounds it works well in "straight" modes over a wide range. For vocal sounds in particular, it may be necessary to preserve formants and for this you are recommended to use OCTMOVE if possible.

PITCH SHIFT is an effective way of transposing just part of the spectrum.

OCTMOVE works well in transposing a steady-pitched sound, preserving formants without producing artefacts. This is because the pitch tracking has been done already by the pitch data file. However, in a complex sound of varying pitch, it is likely to give a wildly changing transposition!
To obtain unsupported transposition intervals, try running the program more than once, e.g. Up x 3 followed by Down x 5.

TRANSPOSE-TRN can only work where a definite pitch trace has been extracted from two sounds, one of which might be the sound to be transposed. One use for the function might be to transpose a steady-pitched source, tracking another sound's varied pitch. Pitch traces from the two could be combined to make a transposition file which could then be applied to the source.
(
Soundshaper's structure requires this to be a separate function. In CDP HELP, it is documented within Transpose and Transposef.)

Note that a combination of SPEED and TIMESTRETCH (q.v.) can also provide a transposition without changing time.

© Ensemble Software and Composers Desktop Project 2012