If all vowels in your English are pronounced fully and clearly, then this may come across as exaggerated and unnatural. It also means that syllables and words can receive a confusing emphasis. If you say I can play a Darbuka drum and pronounce all vowels with a similar effort, then you are emphasising the word can and thus the fact that you are capable of playing this instrument, as if someone has just suggested you are not. You are also emphasising the word a , which might suggest that you are emphasising that you can only play one at a time. This involuntary emphasising can be confusing.