Here is video by professional euphonium player, John Powell explaining how he plays the Wessex Dolce euphonium spot in tune throughout the range without use of a trigger.
John has also helpfully compiled charts with further explanation
Treble clef
http://www.wessex-tubas.com/wp-conte...reble-clef.jpg
Bass clef
http://www.wessex-tubas.com/wp-conte...-bass-clef.jpg
You can hear John Powell with the professional tuba quartet Tubalaté playing Wessex euphonium and tubas live at Frankfurt Musikmesse on the Unplugged Stage, Galleria, Ebene 1, Saturday 9th April at 13:30 and Sunday 10th April at 16:30.
Also at ITEC (International Tuba and Euphonium Conference) in University of Tennessee-Knoxville for final part of opening night concert on May 30th at 8pm
You can find out more about the Dolce euphonium at;
UK - http://www.wessex-tubas.co.uk/product/dolce-euphonium/
USA - http://www.wessex-tubas.com/euphonium/