R2-D2 : the rough mix you heard is not directly about sound samples playback but "hard" transition between 2 playback sampling rate (ie speed for playing the sound files). The pitchshifting was activated in this configuration AND I configured the activator switch so that I don't need to push the button when I power the saber => it automatically goes on after boot (only way to go when you're holding the camera on one hand, I had no tripod).
The problem here is that the orientation of the saber should be measured BEFORE starting the saber which is supposed to be OFF when you power it up. Here, the saber start at normal speed for playback just after power up, then just after the power up sound, it founds out a new orientation of the hilt/blade and lowers the pitch => hard transition.
I may have a trick to get over this, even if it's not a regular situation.
BtW, normally, this feature to get the orientation of the saber at startup to decide of the playback speed is GREAT ! Put the blade down and power the blade, playback speed is slowed down and blade ignition as well. Just like in the movies, as xwing said once : sometimes, the blade will lightup very slowly. Start the saber with the blade up : normal ignition speed and sound.
If you want to hear a normal power on sound to hum transition, watch the video at 3min10.
thanks for you nice feedback, and I'm glad people can understand my english (spoken) !