Jimmy Smith

I notice something on various Jimmy Smith CDs and on a reel to reel I listen to that is unpleasant. When he plays his organ there is often what sounds like severe distortion. This happens during loud or soft points, but more often at loud points in the music. Is this just the way his organ sounded or are the recordings flawed? I can't imagine that all of these recordings just happen to be flawed.

If this is just the way his organ sounded, was he trying to get that sound or was there some other, uncontrollable factor? Has anyone here seen him live that can confirm wether the nasties are or aren't an artifact of the recording?