Swing Timing is a common rhythmic feel used in Blues, Jazz, and plenty of other styles. It can liven up a relatively simple piece of music by adding a continual "ebb and flow" to the piece. Let's check it out!
Essentially, "swing" is a pattern of a long note followed by a short note. Most commonly, we'll be dealing with 8th notes here.
Since two 8th notes add up to the length of one quarter note (one beat in 4/4 time), there is an opportunity to play with the length of the 8th notes.
Rather than playing them both with strict timing, we can extend the length of the first 8th, and then shorten the length of the second 8th. You can toy with the timing of the two 8th notes as much as you like, as long as they still work out to one beat when added up.
This means that swing is open to interpretation, to some degree, by the musicians playing.
However, there's one interpretation that's most common by far. This is going to be what almost everyone is referring to when they describe playing with swing.
Here, we're playing a quarter note followed by an 8th. Notice that they're in triplet form though.
A quarter note + an 8th note in triplet form is exactly one beat!
If this is hard to understand, remember that a quarter note could be broken out into two 8th notes. So it's no different than a group of three 8th notes in triplet form, with the second 8th note tied to the first.
As you can see in the image, we can count this as:
One-and-a, Two-and-a, Three-and-a, Four-and-a.
Playing this along with a metronome, you want to be saying a number each time it clicks. If you can do that, you've got swing timing down!
Now that you understand the concept, let's put it to use! The 12 Bar Blues almost always makes use of swing, and it's a great place to get started.