Back from the rigours of the road (sex and drugs and jazz'n'roll), Dave Stewart gets heavily into rhythm, man, and puts all those odd little bits and pieces into perspicacious perspective.

Phil Sutcliffe once wrote a review of a National Health gig in which he mentioned some of the funny time-signatures the band used, eg ³³₃₇. Now, Phil's a good writer and a nice bloke, but what he wasn't to know is that (thankfully!) there is no such thing as ³³₃₇ time. If there was, I don't think anyone would be able to play it. I hope Phil's reading this as I intend to throw the whole immensely complex and baffling matter of rhythm into crystal clarity with a few pompous strokes of my pen.

Different length notes are written in different ways, and each has its own (often hilarious) name. For example, this type of note

is a minim. This

is a crotchet, and this

is a quaver. Of the three, the minim

is the longest. In each minim there are two crotchets

and in each crotchet, two quavers:

This gives us:

a neat little hierarchy.

Given that, it follows that a minim is twice the length of a crotchet, and that a crotchet is twice the length of a quaver. It also follows that a minim is four times the length of a quaver.

Now this doesn't tell you anything about the speed or tempo of the notes, only their relative lengths. The tempo of a piece will usually be indicated by

= 108 or

= 100 or something like that. This simply means that in the first example there will be 108 crotchets per minute, and in the second 100 quavers per minute. Obviously if there are 108 crotchets a minute, there will be 54 minims, or 216 quavers. If the tempo were

= 120, there'd be two crotchets every second.

For longer notes, we have

, which is twice the length of a minim, and is called a semibreve. Twice the length of a semibreve is a breve, written

, though this is fairly rare.

For the shorter notes, we take the quaver and sub-divide it by adding 'tails':

is a semiquaver (two in every quaver),

is a demisemiquaver (two in every semiquaver) and

is a... wait for it... hemidemisemiquaver. That (thank heavens) is as far as it needs to go, because even at the slow tempo of

= 60 a hemidemisemiquaver would be incredibly fast, 16 of them per second. No-one can actually play that fast accurately, so it's a bit irrelevant; but by all means amuse yourselves with thoughts of millimicroquavers and nanoquavers.

All this adds up to the pyramidal diagram below: (see fig 1).

Consecutive quavers are often written with their 'tails' joined for visual neatness (eg

instead of

instead of

This applies to semiquavers, demisemiquavers and hemidemisemiquavers as well:

American musicians won't understand all this crotchet and quaver lark. To them

is a quarter note,

is an eighth note, etc.

(a semibreve) is their whole note. In a way I suppose that's easier, but I rather like the names myself.

Going back to what I said earlier about ³³₃₇ time; when you read or write a piece of music, there should always be a 'time signature' indicated at the beginning. This takes the shape of two figures, one above the other (rather like a mathematical fraction but without the intervening line), which tells you how many beats there are in a bar and what type of beats they are (crotchets, quavers or minims etc). A bar is a rhythmic subdivision, marked out with bar lines:

The most common time signature is ⁴₄ (sometimes called Common Time), which consists of four crotchets per bar:

All time signature symbols are written in a sort of code; the bottom number tells you the type of beat, the code for crotchet being 4. The top number tells you how many of these beats there are in a bar. Therefore ⁴₄ means:

³₄ would mean three crotchets per bar:

and ⁵₄ is five crotchets per bar:

Now the code for a quaver is 8, so a time signature of which the lower number is 8 tells you that there are so many quavers in a bar. ⁶₈ means:

Similarly the code for a semiquaver is 16, and that of a demisemiquaver is 32. If you look back to the big diagram, it becomes clear that the code for minim has to be 2. So if you see a time signature like ³₂, it means three minims in every bar:

You don't have to be much of a mathematician to work out why ³³₃₇ time is an impossibility!

If you bear in mind the 'code' explanation, it makes rhythms like ¹³₈ seem a little little less intimidating. ¹³₈ is simply 13 quavers per bar, which, while it might be a little hard to play at first, is certainly not difficult to understand.

One more thing about time signatures; in a lot of music (say, for example, Three Blind Mice, a wonderful historic tune which we all know and love) the time signature will remain the same throughout the piece. In the case of Three Blind Mice the time signature is ⁴₄, and this will be written once, at the beginning of the piece, immediately after the clef and the key signature. All the bars thereafter will be ⁴₄ bars; that is, adding up to four crotchets. In other types of music, though, the time signature may change during the piece, and may even differ from bar to bar. For example:

Each time the time signature changes it has to be indicated at the beginning of the bar. With consecutive bars of the same length, the time signature can be omitted:

So the time signature always applies to all ensuing bars unless contra-indicated.

Finally, don't be confused by what I've said about the 'code' system. A ⁴₄ bar is basically a bar with four crotchets; however, that's not to say that it couldn't have eight quavers, or two minims. Or even six quavers and four semiquavers. As long as the total adds up to the equivalent of four crotchets, it'll be a ⁴₄ bar!

I hope this all makes sense to you. Rhythm is a bit difficult to understand at first and if there's anything here that doesn't seem right please write to me c/o Sound International. I'll try to clarify any problems!