Ok that way of input note begin to answer to my need :
It is ok but not exactly what I had in my mind.
In a future evolution it would be great to be able to play non pitched chords.
For instance considering a musical line with a crescendo : first input the rhythm on the midi keyboard pressing CD CD CDE CDEF CDEFG… then input the right notes chords pitches but step by step, again on the midi keyboard CD CE ACF GCEG FACFA…