Roel,
Roland uses the "release velocity" already, in synths like the XV 3080; a good example is an acoustic guitar patch, where the release velocity controls a partial that has only fret noise. The overall effect is very realistic.
Would you like that I post an MP3 using that patch?
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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.