The ukulele shuffle strumming exercise on the previous page presents a challenge to some students of the ukulele. Some people can do it, but don't really understand what is happening, and some people get thrown off completely, and have a difficult time aligning what their ear hears, with what their finger does.
Because shuffles are such a common part of modern music, and include anything we might call "Swingin'", we're going to look at these "off-kilter" rhythms in a little more detail, to help you understand what a shuffle is, how it differs from a "straight" rhythm, and what exactly you do to create, emulate, or follow one.
By engaging both your eyes and your ears, this demonstration will be processed in a larger swath of your brain, and hopefully help you see more clearly what a shuffle is. The better you understand it, the more easily you will be able to forget about it and focus on the music.
Press the "play" button on the demonstration below, and watch as a steady-moving time marker travels across the down-strokes and up-strokes of a straight rhythm, and then a shuffle.
As you can see, the time between the up and the down, and the time between the down and the up, is the same for a straight rhythm - but in a shuffle, the time between the up and the down is much smaller than the time between the down and the up. Another way to say this is that your hand will be spending more time in the "down" position between strums than in the "up" position between strums.
And you can't really quantify this. In a classical "swing" rhythm, in theory, the space between the downs is divided into 3 - the down is on the one, the up is on the 3, so the time before the up is twice as long as the time after the up.
But in the real world, and even in really, really swingin' swing rhythms - it's all about feel. Some shuffles are soft, some are hard, some are swingin', some really rock, and the feel of the shuffle has to do with which beats, (and ups) are accented - and at what microsecond between the downs the ups actually fall.
As you play more and more things that "shuffle", you will find it easier and easier to "get into the groove" - which is the non-mathematical way of saying that you will instinctively and easily be able to play the upchucks on precisely the microsecond that the groove of the song calls for. (Bands that instinctively play the upchucks together on really cool microseconds are usually referred to as "tight".)