Here is one way that I have gotten spectral UGs to help
with pitch tracking:

;While this is not a complete .orc file, it represents the heart of a 
;pitch-tracking instrument that reads input and spectrally extracts 
;the fundamental using octdown, noctdft, specsum, and specptrk.

;William Kleinsasser
;Towson University
;Baltimore, MD

;--------------------------------------------------------------------------
;INITIALIZE VARIABLES
;--------------------------------------------------------------------------     

;SET MANUALLY:
ianalperiod = .01                       ;set period for spectral 
analysis
ianalsamps      = ianalperiod*sr        ;set number of samples in 
spectral anal

;FROM SCORE:
ipartialcount = p4              ;number of partials for analysis (from score)
inum = p5                       ;soundfile id number (from score)

;--------------------------------------------------------------------------
;READ SOUNDFILE IN (mono)
;--------------------------------------------------------------------------     
;.5 = octave down, 2 = octave up, etc.
;(use ; to comment-out the options you do not wish to use)
;       asig     soundin inum     ;read soundfile "inum"
;       OR
        asig     soundin "soundfile_name";read soundfile "file name"
;       OR
;       asig     in         ;real-time sound input from ADC
        
;--------------------------------------------------------------------------
;ANALYZE THE SPECTRUM
;--------------------------------------------------------------------------     
;downsample in 6 octaves:
        dsamp   octdown asig,6,ianalsamps,0     
                                
;calculate 72-point dft (dB):   
        wsig    noctdft dsamp,ianalperiod,12,33,1,1,1   
        
;sum the spec bins, and ksmooth:
        ksum    specsum wsig, 1                         
                                
;analyze for pitch-tracking:
        koct    specptrk wsig, ipartialcount, .8, 0     
        
;set kpitch to = the tracked pitch in cpsoct mode:
        kpitch = 
cpsoct(koct)                                                   


                                                                

;**************

On Thu, 26 Jun 1997, Mike Berry wrote:

>       The spectral operators, as far as I know, don't do anything,
> other than supply each other with data.  They do not interact in any way
> with other csound opcodes.  So you can't use them to in the way you are
> describing.
> 
> Mike Berry