I'd question whether any sound can be charismatic - perhaps the OP meant 'charming'? However I'd also vote for the A400M as having a charming sound; Dart Heralds, 748s, F-28s etc are evocative for me but not charming. However I do recall the Argosy sounding a bit more tuneful than the Viscount, despite having basically the same engine/prop layout. Again, charming, not charismatic.