What are the techniques of puting runs in any given worship song. How do you know how many notes are needed. I always wanted to know how awesome or real experiences musicians but runs in thier songs. Does it depend on the key and how well you know your scales. I know All my scales I just dont use runs in my songs, can you please help me LGM FAMILY. 
The style of your play may dictate whether or not you use runs/trills...they are not necessary, every musician is different. A run (use of your scales right or left hand) can be done almost anywhere in a song if rhythm/timing is kept. However, too many runs IMHO often will kill a song. Start with simple scale notes in right hand over your left hand chord in rhythm to start getting a feel how a run should be played...then try to speed the right hand double-time over the same left hand chords in rhythm. Hope this helps a little...Be Blessed!
