Amelia from Georgia asks, "What do time signatures in music mean?"

Great question, Amelia. I'm going to give you a little more info than you asked for; I'm going to give an answer to your question, and then I'm going to give you some examples of some unusual time signatures in musical compositions.

A time signature is a pair of numbers that you'll see, always at the beginning of a piece of sheet music, and sometimes in the middle of the sheet music as well, since some musical compositions have more than one time signature. Here's an example of a fairly common time signature in the picture to the left.

What exactly do these numbers mean? Well, the bottom number means that a quarter note gets a beat, and there are three beats in a measure. That may or may not help you understand, depending on what music terminology you understand, so let's break that down a bit.

A Beat is the basic unit of time in music. It's like the pulse, or the heartbeat, of a piece of music. If you're clapping along with a piece of music, then there's a good chance you're clapping on the beats. If you're tapping your feet, you're doing the same. If you hear a band playing, and they start off by saying, "1 2 3 4" before they start playing, that counting is helping to set the heartbeat of the music. If you're listening to a drummer, you'll probably hear drum strikes that aren't on the beat, but you'll definitely hear the kick and the snare on the beats. The underlying pattern in most songs is kick-snare-kick-snare over and over again (with other things mixed in). that kick-snare pattern is what sets your toes tapping.

A Measure can be thought of as another unit of time in music; a measure is a set or group of beats. In most music, every measure has the same number of beats, and the first beat in a group gets more emphasis than the others. Sometimes a beat in the middle of the measure will get some emphasis as well. Going back to our example of the kick-snare-kick-snare, that bass drum kick is the emphasis (you could think of it as KICK-snare-Kick-snare/KICK-snare-Kick-snare/etc.), and it repeats over and over throughout the song. In music, measures are defined by a vertical bar right through the middle of the musical staff, like this:

You can see those vertical lines before the words "world," "Lord," "come" and the second syllable of "receive." Those lines mark of groups of beats. And if you were to sing this song aloud, you would realize that the words (or syllables) immediately following those vertical lines are the ones that receive the stress or accent.

We have one more thing we need to explain in order to fully understand a time signature...note names. Take a look at the chart below:

In this chart, the notes, from left to right, are: "whole note," "half note," "quarter note," "eighth note," and "sixteenth note." Why are they called those? Because in the most common time signature (4/4 time), a whole note takes up a WHOLE measure, a half note is HALF of a measure, and a quarter note is one QUARTER of the measure. Of course, if you're not in 4/4 time, that's not true, but the name has stuck. So if you see a 4 in the bottom of a time signature that means a quarter note gets one beat. If you see a 2 in the bottom of the time signature, that means a half note gets one beat. If you see an 8 in the bottom of the time signature, that means an eighth note gets one beat.

Okay, with all of that behind us, let's go back to the original example of 3/4 time. The three means that there are three beats in a measure, and the four means that a quarter note gets a beat. So if you were clapping this one, you would do "CLAP-clap-clap-CLAP-clap-clap," and each "big" clap is the beginning of a new measure. If you were playing the drums, you might play "KICK-snare-snare-KICK-snare-snare."

Interesting Time Signatures

The majority of music you'll listen to is written in 4/4 time (four beats per measure, a quarter note gets a beat). Some will be 3/4 (which is often referred to as a waltz), or 6/8 time (six beats per measure, an eighth note gets a beat - this is the common meter for Irish jigs). Once in awhile you'll hear something that's a bit different.and I've selected a few that you can listen to on youtube.

Of the Father's Love Begotten - since I've already brought up a Christmas song, here's another - an old old Christmas hymn. If you look at sheet music for this one, you'll likely find that the publisher hasn't even bothered trying to put a time signature on it, and has more-or-less given up on doing measure markings; the measure markings are actually just phrase markings, and every phrase is a different length. The link I've provided has no singing, but does show the sheet music.

Waltz from Tchaikovsky Symphony #6 - This one is called a waltz, but it is not in the normal 3/4 time; it's in 5/4 time instead. This means that it has 5 beats in a measure, which gives it a slightly off-kilter feeling because our brains aren't used to processing that kind of rhythm. It's a beautiful, elegant piece of music.

Finale from Stravinsky's Firebird Suite - My introduction to this piece of music was in high school when I participated in the All-State music festival. In the linked video, the section in an unusual time signature starts at 2:00, but it's interesting to listen to the lead-in to that, so it's worth listening to the whole video. The unusual time signature is 7/4 time. I remember looking at the sheet music and thinking, "What in the world?" because every measure was subdivided into groups of 3 beats and 4 beats - presumably to help us get the count right! 

The Dargason from Holst's Saint Paul Suite - This one I played in university orchestra, and oh, was it fun! What makes this piece so unusual is that there are two melodies going on simultaneously, and they are in different time signatures. One melody is "Greensleeves," which is in 3/4 time, and the other is a jig, which is in 6/8 time. Now, as a mathematician, I notice that these two fractions - 3/4 and 6/8 are equivalent. This means that the measure marks fall in the same place for each melody, but what happens in the middle of the measure is quite different.

Here Comes the Sun - In general, the Beatles were notorious for shifting into unusual beat patterns. I've picked "Here Comes the Sun" as an example. You can feel the 4/4 beat through most of the song, but when they get to the bridge, everything seems to go haywire. I haven't looked at the sheet music for this one, but Wikipedia says that the bridge goes through the following rhythm structure: 11/8 + 4/4 + 7/8.