Many non-Arabic speaking choristers finds pronunciation of certain Arabic letters difficult, especially the letters ص (s), ض (d), ط (t), ظ (z), and ق (q).
Below is a link to a useful website with a flash video that should help our choristers master the use of these letters.
http://www.arabicpod.net/learnarabic/lesson/91/Letter_pronunciation
Click on the link below, then click on Visual Tutorial (as illustrated)
Andalus Arabic Choir 