A Study in Pink

I found this code . it generates glissandi. On the other hand, it is very difficult to have a control of this code. I simplified It. I would want to ask beginner’s question.
The code is the following one:
(defmacro sweep (dur)
(stretch-abs 1 (mult (pwl 0 0.8 dur 0.05 dur)
(hzosc (sum 440 (mult 3360 (ramp dur)))))))

(defun lowpass (sig hz)
(force-srate (* hz 2) sig)(snd-srate sig)))

(s-rest 1) (s-rest 1)
(at-abs 15 (lowpass (sweep 4)840))))

Would it be possible to use this random effect hanging a few seconds of a sound? Let us imagine the following sinusoidal sound:
(scale 0.5
(osc (hz-to-step 697) 19)))

It would be possible, for example, to allocate to the sound these glissandis during 4 seconds. Of time t1 = 4s in time t2 = 8s for example. Before t1 and after t2, we would hear that the sound sisnusoïdal.
Beforehand thank you for the information.

Topic split.
Please do not add new questions on the end of unrelated topics.

I would have given your topic a relevant topic title, but I don’t understand what you are asking.

Also, please use code tags around any included code - it makes it easier to read and preserves the code layout.
If you click on the “Code” button (above the message composing box) it will insert [c_o_de][_/_code] at the cursor position.
Then type or paste the code between the two “code” tags like this:

[code];code goes here


Also, when quoting code, please include a link to where it came from - it can be helpful if we can see the example in its original context.