Yeah, Neamanson. It is pretty straight forward for 2 reasons. Melodies that you are familiar with, and predictable chord progressions. A bit like the easiest way to learn to ad lib instrumentally is on a straight blues progression. You know where it is going all the time. Try to follow celtic music if you want to go batty trying to predict harmonic progression. It is totally unpredictable to our American ears and does not dwell on the 1,4, 1, 5, 5(7th) stuff that we sort of know at a primitave level. Celtic harmony is frequently 1, 7 ,1 sort od pregression that is a bit like having a staircase with the steps spaced randomly. But Gospel is definately a nice place to get harmonies locked in your head.