Bernie, you've opened up a great topic, one that's probably not discussed enough. Gary's right....sort of. Don is a good example of ACCENTING (ie. playing riffs AROUND the vocals) as opposed to pure COMPING which is more playing BEHIND the vocals. BB King is a great example of ACCENTING. Pianist in Big Bands tend to do BOTH. Best statement so far...."It's not an exact science". Critical listening and analysis of what the 'masters' are doing is probably the best (maybe only) approach to learning this 'inexact science'. BTW, playing with other musicians using only 'fake sheets' will force you to learn what to do .

chas