The S1 and S2 also had different engines with some changes that may be pertinent.

The 286bhp in the S1 was a single camshaft profile and has an even power profile.
The 330bhp in the S2 does certainly come more on-the-cam above 4000 causing a louder step in the noise from the sidepipes.

The S2 sidepipes (single) are modestly loud under idle and smooth cruise. They get loud according to the revs and how wide open the throttle is. In reality they would seem to be the best combination of loud when needed.

The Coupe sidepipes (dual) are LOUD under all settings. Very loud to shocking under fully throttle/high revs. As you outline the note is very deep and so pulses off windows etc. I was in an underground car park a few weeks ago, I backed into a single parking slot with concrete walls on three sides. During this moment at least three car alarms in the facing row got set off. Full on Marmite, either you thrive at the naughty or you wonder what kind of loon would do it.

Everyone loves a Morgan. Even me, unless it's broken again.