Swing Feel is Just a Matter of Time -

.... but not very much, as it turns out. 
    Jazz students often have trouble with swing feel, and while I'm not going to solve that problem here, I was curious how much difference there really is between playing STRAIGHT and playing SWING.  Of course, there are different DEGREES of swing - lines can be heavily swung or lightly swung, but for now let's assume that swing is this -- the 1st and last notes of the underlying triplet  --this would be a fairly heavy swing feel. Notice that in swing feel, the second half of every beat is slightly later than it would be if played straight ( swing feel is "stems down", straight feel is "stems up", X is the difference between the placement of the 2nd notes, the "offbeats" - in this case eighth- notes that fall between the beats)

Swing Feel as the 1st and last notes of a triplet

What is the value of X?  That is my interest here, out of mere curiosity to get a sense of the subtlety that's required to differentiate straight playing from swing playing.  Here is a single beat expanded to make the puzzle clearer:

Let's assume a tempo of quarter-note = 240 beats per minute ( a common swing jazz tempo, though a pretty good clip).   I'll give you the answer here and show the number-crunching below.

It turns out that
                                 X = 1/24 sec   or  .041 seconds
Jazz players are expected to be THAT accurate when placing in time the 2nd half of every beat.  Think about subdividing 1 second into 24 parts - pretty well impossible to do consciously!  For comparison,  lowest string on the piano vibrates at 27.5 vibrations per second!  It's no surprise that people have trouble learning the placement of the off-beats in Swing.  And some technical skill is required just to play THAT accurately.

Here are the numbers if you want to follow the calculations.   

  At 240 beats/minute, each beat spans 1/4 second  240 beats/60 seconds = 4 beats/sec

       or,    1 beat = 1/4 sec

Therefore     a+a = 1/4 sec     and b+b+b = 1/4 sec

  or    a = 1/8 sec   and b = 1/12 sec

x = b + b - a  = 1/12  + 1/12  -  1/8

   or   x = 4/24 - 3/24   =   1/24 sec

To really learn Swing feel - Listen to the Count Basie Orchestra