Many thanks to you.
@rorywalsh : no worries, things will find a solution.
@gsenna : My keyboard is a ALESIS VI-49, I did indeed monitor with MIDI-OX . All notes are sent with a note on and a note off message. So the keyboard is not buggy.
Once I have triggered the bug with the real midi keyboard, then I can repeat it with the virtual keyboard, on the same note.
When printing all messages received by the instrument, it indeed receive all note on and note off.
I also changed the computer from my tablet to my big Tower (core i7) .. I get the same trouble after a while.
It seems to me that, Cabbage forgets from time to time to send a note off to Csound. (I discovered today that there can be a residual sound with all previously played notes, as if some buffer was never cleaned, despite the fact that I clear all audio variable at the end of the instrument).
The csd and the howto are in this post : http://forum.cabbageaudio.com/t/new-synth-beta-morpheur/727/3
Even if it seems to be big... in fact all audio is in instr 1, the rest is for GUI and keyboard management and effects. I also tried to comment a lot.. for further maintenance
Please feel to try it and thank you a lot for your help.