I play rock organ too. Jazzmammal is exactly correct. If it’s a crash ending, depending on how wild the song was and how long the drummer stretched the end out, I play 7th and 9th chords, I slide up to the 13th of the chord, I lay my arm on 2 octaves of low notes and start and stop the Leslie.

There’s no way to get BIAB to do this, unless crash endings are part of the next RT style set.

That is a nice offer from Jazzmammal. If you post the end of your song, I would be happy to send you a recording also.