On Saturday I attended a free 1 1/2 hour concert by The Positively Testcard, featuring Dave Woodhead on whistle.
Dave played almost exclusively on Shaw whistles, D, C and Bb, and just one tune on a Feadog D Mk 2. He told me that after spending hundreds on various of whistles (he mentioned Overtons) the Shaws have become his favourite, because they work best for kwela, allowing overblowing & other tricks to get the kwela sound.
To play kwela, Dave puts the whistle into his mouth twisted sideways about 45 degrees, with the window just outside his lips.
The band played many tunes from their two CDs, plus several new tunes including two mandolin lead tunes. They will be assembling a new album soon.
There were 30-40 people waiting for the concert to start, and many more assembled once the music started - the concert was in the foyer of The National Theatre on the Southbank(this is common practise) and next to the cafeteria, so many passers by caught the sounds and stopped to listen. A few people were so taken with the beat that they started dancing, though I was too shy to join them, settling for polite applause at the end of each number.