Take a look at Brett Manning’s Singing Success vocal training course. I used this at my last church and really enjoyed the program. I’m no singer but I added a full note to my limited range, and I only half-heartedly did the exercises. Brookwood worship leader Steve Smith says he added 5 notes to his range. When UK worship leader Tim Light was visiting over here one time we went up to Nashville and had a lesson with Brett – I’m very impressed.