1. Timing and groove: We are taught to play swing 8ths like triplet 8ths, or even dotted 8ths and 16ths. Even today you'll see swing taught like this:
But this is wrong in the modern era. That notion comes from the 1920s and '30s when swing was brand new, and it has stubbornly stuck around in casual circles. But real jazz players don't play swing 8ths that way.
Modernly, swing 8ths are played closer to straight 8ths, with the length difference between two eighths in one beat getting more "straight" as the tempo increases. Indeed, the more compelling groove modernly is to play them almost even. That sounds more hip, cool, and sophisticated. Playing them with the old rhythm sounds corny and stilted, modernly, and should be avoided unless you're trying to play in a specific 1920s style.
2. Emphasis: I can't tell you how often I hear legit and amateur trombonists put emphasis on the downbeats -- first of the two 8th notes in a beat -- which gives a very up and down feel, an almost marching band square groove. If you've ever heard Joe Alessi try to play jazz, you've heard this.
Downbeats are naturally the strongest beats in music, and to emphasize that further by playing the downbeats stronger gives a very stilted feel to the music, which defeats the whole notion of swing. Jazz should have a rolling feel. And the way to do that is to de-emphasize the downbeats and to put the emphasis on the 2nd 8th note in each beat. So, in a run of four 8th notes you would emphasize (play louder) the 2nd and 4th notes, the off-beats. Indeed, often you can almost ghost the 1st and 3rd 8th notes (on the beats). Modernly, we emphasize the 2nd and 4th eighth notes (the "and" of each beat), and we simultaneously emphasize the 2nd and 4th beats in the measure. Not the 1st and 3rd.
Emphasizing the off-beats makes it feel like the notes are falling into the next downbeat, which gives a far smoother and more interesting jazz feel. It's almost like a suspension and resolution, the way emphasizing the off-beats works in leading one beat into the next. This can take a minute to get the hang of, but putting the emphasis on the off-beats gives you a great and natural jazz groove.
3. Putting it together: Emphasizing the "and" of each beat and the 2nd and 4th beats of the measure while playing the notes closer to straight 8ths is the modern way to swing. In fact, with the off-beat emphasis you can swing quite hard while playing absolutely even 8ths at a moderate tempo or faster. So ditch the marching band strength of the downbeats in favor of the rolling suspension-resolution feel of movement and you'll sound like a real jazzer.
Thanks for coming to my TED Talk!
