Easiest answer: listen to Tony Decap pronounce his name in this video
from about 1:40 onwards: https://www.youtube.com/watch?v=fwd8sJYvziA 

Regards,
Thijs Haenen

 [ Be sure to hear the organ at the beginning of the video -- it sounds
 [ wonderful! At time 1:40 Tony Decap is telling of his forefathers,
 [ all named "Decap." -- Robbie