Alain,
I assume that you first pressed "Other", then "Keyboard mode" then "Options". At this point, on the right of the screen, you have a slider: you can set the velocity to "High", "Medium" or "Low". High means that you have to hit the note hard (i.e. with a High velocity) to hear the sound, while Low means that you have almost no velocity response: you just hit the note and it sounds almost at the maximum level (like an organ). So this is the right setting for you. After setting the slider down to "Low" you have to save the User Program (press twice the first button on the right). If you wish, you can repeat the same operation for Upper 1, Upper 2, Lower 1, Lower 2, Manual drums, Manual bass and Variphrase.
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Korg Kronos 61 and PA3X-Pro76, Roland G-70, BK7-m and Integra 7, Casio PX-5S, Fender Stratocaster with Fralin pickups, Fender Stratocaster with Kinman pickups, vintage Gibson SG standard.