>I however wanted to create "from scratch" those things (i.e.
>pitch and freq shift algs...)

Here is a crude harmonizer made way back when I was using Csound Ver. 1.0 
to "tune" sampled soundfiles. It is tedious to work with and you
have to trim out the silences the delay line puts in, but it was all
I had at the time and it got the job done.

(Supply your own soundfiles!)

-Tom

;;;;;;;;;;;;;;; hrmnzr.orc
sr = 48000
kr = 24000
ksmps = 2
nchnls = 1

instr 1                     ;sample pitch shifter
       idur = p3
       ifilno = p4
a1 soundin ifilno
k2 line p5,p3,p6
k3 linen p7,0,p3,.02
  a2 delayr 1
  a3 deltapi k2
  delayw a1
out a3*k3
 endin

 instr 2                   ;sine ref freq
 i1 = cpspch(p5)
 i2 = ampdb(p4)
 k1 linen i2,.04,p3,.02
 a1 oscil k1,i1,1
  out a1
  endin



instr 3                       ;playback
        idur = p3
        ifilno = p4

a1 soundin ifilno
  k3 linen p5,0,p3,.02
     out a1*k3
  endin










;;;;;;;;;;;;;;;;;;; hrmnzr.sco
f1 0 1024 10 1

;tuning: t1 > t2 sharps pitch
;tuning: t1 < t2 flats pitch


           sf#  t1   t1  amp 
i1 0 11.78 17  .9    .2   1   

i2 0 4  72   7.02 ;reference tone

e