How sad to think that any correspondent to this forum could confuse the sound of a RR Tyne, with its chordant twin spools, the matching descant of its two wheelcases, the purr of the centrifugal breather, the hiss from the long elegant prop blades and the base sounds from the jet pipe - with that stinking little Alison 501, belching smoke, bleeding air and beating the air into submission with those fat little chopped off props.