The Complete Idiot''s Guide to Music Theory

Par t 1:Tones

If you think other musicians might be confused about whether a note has

reverted back to normal, it’s okay to use a courtesysharp, flat, or natural sign.

(This is a sign placed within parentheses.) This reminds the reader that the note

has reverted back to its normal state. You don’t have to use courtesy signs like

this, but when the music is complicated, it can be quite helpful.

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A courtesy accidental reminds musicians that a changed note has reverted back to normal.

Changing Keys

Some long pieces of music don’t always use the same key throughout the entire

piece. In fact, some short pop songs change keys midway through. It’s allowed.

When you change keys in the middle of a song, it’s called modulatingto another

key. You can modulate to any key, although the most common modulations are

up a half step (from E Major to F Major, for example), or up a fourth or fifth

(from E Major to either A Major or B Major, for example).

When you want to change keys, you indicate this by inserting a new key signa-

ture in the first measure of the new key. It’s as simple as that, as you can see in

the following figure. (Note that some composers and arrangers also insert a

double bar whenever there’s a key change.)

The half-step modula-

tion is most common

in twentieth-century

popular music, and

can add a “lift” to the end

of a pop song. The fourth

or fifth modulation is more

common in classical music

of the seventeenth through

the nineteenth centuries.

Tip

To change keys, insert a new key signature.

The only complicated key change is when you’re changing to the key of C—

which has no sharps or flats. You indicate this by using natural signs to cancel

out the previous sharps or flats, like this:

If you want, you can alert musicians to a key change by placing the

appropriate sharps and flats at the very end of the last staff of the old

key—as well as with a new key signature in the following measure. This

approach is entirely optional; it’s perfectly acceptable to signal the key

change with a single key signature in the first measure of the new key.

Tip