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SOUNDSHAPER: CDP REFERENCE

TUNE - tune the spectrum to a given chord


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SPECTRAL > FREQ/PITCH > TUNE(VARY) >

SUMMARY
Re-tunes the spectrum to specified pitches (and their harmonics).
From a text file of specified frequencies or MIDI pitches, TUNE adds their harmonics to create an overall template set of frequencies. Existing frequency values are adjusted to the nearest frequencies of the template (focus parameter) and other frequencies are suppressed (clarity parameter). 
There is also an optional trace parameter and a frequency divider ( bass cutoff), below which the frequencies are not tuned.

In the CDP7 extension tunevary (not LITE), the tuning can be time-varying (see Mode 3).

MODES
 1. Frequencies: Tuning data file gives frequencies (program adds harmonics).
 2. MIDI pitches: Tuning data file gives MIDI pitch values (program adds harmonics).
 3. Variable Pitch (MIDI): Time-varying retuning of the spectrum (CDP: tunevary).

PARAMETERS
 freqdata (Mode 1 only): tuning text data file (.tun) listing a set of frequencies.
Values in Hz.; fractional values are allowed. 
Example - A440 and some 8ve transpositions:
220
330
440
550
 mididata (Mode 2 only): tuning text data file (.tun) listing a set of MIDI pitch values.
Values: MIDI pitch (1-128); fractional values are allowed (e.g. 64.5).
Example - chord of A major:
57
64
69
73
76
 [focus]  Degree of focusing of pitches onto the template.
Range: 0-1; CDP default: 1. Recommended: 1. T-V  
 [clarity] Extent to which non-template partials are suppressed.
Range: 0-1; CDP default: 0. Recommended: 1. T-V
 [trace]  Number of spectral components to retain/retune per analysis window (less prominent spectral channels are lost).
Range: 1-no. of analysis channels (e.g. 1-1024) T-V
 [bass cutoff] : tune only frequencies above this and ignore all lower ones.
Range: 9-22050 Hz. T-V  

 varipch (Mode 3 only): data file consisting of lines of TIME  MIDI_PITCH1, [MIDI_PITCH2,...]
   Each line must have the same number of pitches.
   Ranges Time: 0 - file-length (secs)
              Midi_Pitch: 1-127 (Mid C =60)

 

NOTES

In most cases, TUNE produces a very natural-sounding re-tuning. The general spectral envelope and dynamic articulation of the original are unaffected: if an appropriate channel (one that is retuned and not suppressed) has only a small amplitude, then that component will likewise have a small amplitude. Similarly, the A major example above could tune birdsong without introducing bass components, as there would be none in the original.  

On the other hand, an attempt to tune a c-minor chordal source to a complex chord produced mainly c-minor out: this was because the
source had very weak non-c-minor frequencies and the template's harmonics still contained many components shared with c-minor.  It can therefore be useful to prepare the source by transposition or spectral filtering. Sometimes it is better instead to mix a number of PICKs (each tuned to a specific pitch+harmonics) to make up the desired chord, or to split the chord into smaller units and TUNE each separately.

A more subtle problem is that the program tends to involve some thinning of the sound, leading to amplitude loss and a less defined stereo image. A number of smaller tuned chordal units suitably mixed and panned can overcome this difficulty.
 
The time-varying mode 3 (CDP: tunevary) may be compared with VARIBANK.

© Ensemble Software and Composers Desktop Project 2014