[CM] snd-rt <slider> naming problem

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hi,

I'm working on a model of a tibetan singing bowl with additive synthesis
and I'm trying to write a few functions assisting me with it.
The following function is supposed to take a list of arbitrary length as
argument and is creating a sinus with a few sliders from each element in
the list. The list is as follows:

((frequency amplitude frequency_slider_name amp_slider_name) ...)

so for each list of four elements it should create a sinus with the
given frequency, amplitude and names of the slider.
But the problem is that the <slider> object only accepts strings, not
expressions which evaluate to a string (or so it would seem to me) and
also no variables containing a string.
How am I going to get past that problem?

the error I get is thus:

string-append: wrong-type-arg: Wrong type (expecting "string"): freqname
(freqname)

but if I use string-append like this:

(let ((freq "freq")
      (amp "amp"))
  (print (string-append freq amp)))

it works?!?!  prints --> "freqamp"


My code is the following:

(definstrument (oscillatorbank oscillators)
    (define-multi-instrument-rt-dialog)
    (define* (oscillator-rec oscillators)
      (if (null? oscillators)
  #t
  (let* 
      ((oscillator1 (car oscillators))
       (freq (car oscillator1))
       (amp (car (cdr oscillator1)))
       (freqname (car (cdr (cdr oscillator1))))
       (ampname (car (cdr (cdr (cdr oscillator1))))))
    (begin (<rt-out> (* (oscil* (<slider> freqname (- freq 1) freq (+
freq 1)))
(<slider> ampname 0 amp 1 :log #t)))
   (oscillator-rec (cdr oscillators))))))
    (oscillator-rec oscillators))

(define oscilbank (oscillatorbank '((57.20 0.1 "freq1" "amp1") (175.63
0.1 "freq2" "amp2") (343.89 0.1 "freq3" "amp3"))))

anyone any hints?

thanks