Hello Rod,
If I recall correctly you're using Hauptwerk v5 (as opposed to v6, which has options for 96 kHz and higher-definition pitch-shifting, which would be of benefit in terms of reducing distortion generally, although the Paramount series don't use modelled tremulants, so their degree of pitch-shifting would probably be small anyway)?
I just tried loading the Paramount 450 (in Hauptwerk v6) and turning on just the 'S HORN 8' tab on the Solo division, with no other tabs at all turned on, and I don't hear any beating or other repetitive noise sounds. Do you, even if you have no other tabs at all apart from that one turned on?
Is that the rank you're referring to?
Am I correct in thinking that that particular rank isn't affected by any tremulants?
(Aside from the rank itself, the only other sound I hear is the blower.)
Are you perhaps just referring to a tremulant noise effect, which the various tremulants play intentionally in the background whenever the tabs are on?