this topic http://puredata.hurleur.com/sujet-7818-samvada-ios-sympathetic-strings-app gave me the taste for a sympathetic sitar strings box.

I made a Samvada-like patch, with the info given in the post and in links pointed to by the post.
The seed frequency has been choosen to be similar to the one that can be seen in the demo video of the app.
The effect of the allpass dispersion filter is very subtle (I'm not sure to hear it).
I get many sigsend and receive~ errors due to the feedback loop under 64 samples, but it seems to do the job anyway.
The basic excitation method I used to "pluck" the strings doesn't work for highest notes, the resonance occurs normally though.
Sorry for the many multiplication constants used between "stages", it just came like that ;-). It works well with my violin, would be glad to hear if other instruments need improvement in the levels in the patch.
The "jawari" feedback between output and delay length was fixed to 4%.

Thank you again for the inspiration, Iotic !