First, when editing keygroup parameters, make sure you select ALL keygroups. When you press a pad on the MPC it allows you to edit just the one sample for that note you’re playing. Second, it may be easier to sample it without the filter swell and instead do that in the MPC and have legato on. There may be more advanced ways to achieve it with velocity layers where low velocity notes play the second half of the sample without the swell, so you can play hard when you want a swell and soft when you want it to play smoothly. Third, when all groups are selected go to the main page and set polyphony to mono.
