my book says, the bottom number indicates which note value receives one beat.

so does that mean if its 4 the fourth note will be a quarter note?

if you could explain this it bit more for me that would be great.
Quote by Wrst_Plyr_Evr
the bottom number is what note value is one beat. Ex: If it's 3/8, there's three eighth notes in one measure.

...I think.

Correct.
Q: Favourite Pink Floyd song?
A: The one where they get wicked high and play Emin and A for an hour.
Quote by Wrst_Plyr_Evr
the bottom number is what note value is one beat. Ex: If it's 3/8, there's three eighth notes in one measure.

...I think.

and would there only be three eighth notes, nothing else?
Quote by shredda2084
and would there only be three eighth notes, nothing else?

It would be anything that is equivalent to three eighth notes. Like, six 16th notes, twelce 32nd notes etc. The bottom number just indicates the note value of one count. 4 would be quarter, 8 would be eighth etc etc
It could be two eighth notes and two sixteenth; or one eighth, two sixteenth, and four thirty-second; or one quarter and one eighth; anything that adds up to three eighth notes.
Quote by nazfomo
It would be anything that is equivalent to three eighth notes. Like, six 16th notes, twelce 32nd notes etc. The bottom number just indicates the note value of one count. 4 would be quarter, 8 would be eighth etc etc

ok, i understand now, thats great, thanks
Quote by nazfomo
It would be anything that is equivalent to three eighth notes. Like, six 16th notes, twelce 32nd notes etc. The bottom number just indicates the note value of one count. 4 would be quarter, 8 would be eighth etc etc

Not really. It gets more complicated than that. Time signature tells us what meter the piece of music uses. You will probably come across only two types - simple and compound.

I. simple meters
A simple meter is such one where the beat naturally divides into two (and then four, eight etc.). It may divide into three notes when there's a triplet, but that's not natural in such meters.

These will be meters like 4/4, 2/2, 2/4, 4/2, 3/4, 3/8. The most common is 4/4 and you will come across it in most rock music, e.g. this one:

This meter has four beats and quarter note is the beat. 3/4 has then three beats and quarter note is the beat, like in this minuet by Bach:

In simple meters, the definition that ''top number gives you the number of beats and the bottom number tells you what note gets a beat'' works.

II. compound meters
Here the definition no longer works. Here the beat naturally divides into three and dotted quarter note gets the beat. You will often come across 6/8 and 12/8. The former has two beats, the latter has three. Many of those ballads use such a meter, e.g. Still Got the Blues, Nothing Else Matters:

III.
There are, of course, other types of meters. Here's such a one - additive meter 9/8 (or rather (2+2+2+3)/8). This means it has four beats, but three short (two eighth notes) and one long (three eighth notes). A good example is Blue Rondo alla Turk by Dave Brubeck Quartet. The first three bars are in additive 9/8 meter (like described) and the fourth bar is in a compound 9/8 meter (three beats where dotted quarter note gets the beat). So it goes one two three fooour / one two three fooour / one two three fooour / ooone twooo threee and again...

Good. But I've got two things:

Quote by Slayertplsko

II. compound meters
Here the definition no longer works. Here the beat naturally divides into three and dotted quarter note gets the beat. You will often come across 6/8 and 12/8. The former has two beats, the latter has three. Many of those ballads use such a meter, e.g. Still Got the Blues, Nothing Else Matters:

12/8 is 4 beats... not 3! Probably just a typo though ;]

III.
There are, of course, other types of meters. Here's such a one - additive meter 9/8 (or rather (2+2+2+3)/8). This means it has four beats, but three short (two eighth notes) and one long (three eighth notes). A good example is Blue Rondo alla Turk by Dave Brubeck Quartet. The first three bars are in additive 9/8 meter (like described) and the fourth bar is in a compound 9/8 meter (three beats where dotted quarter note gets the beat). So it goes one two three fooour / one two three fooour / one two three fooour / ooone twooo threee and again...

9/8 is not an additive meter by any means. Even with the way you described it. It is a Compound meter in that it's the Compound Meter's version of 3/4. It gets 3 beats, each with a dotted quarter. Having said that, you could DEFINITELY treat it as if it was an additive meter by using syncopation, but you can do the same thing with other, more common meters, such as 4/4 (the beats could be accented on *(3+3+2/4) among other things).

An additive meter would be something like 7/8 which, among others, is tapped *(3+3+1)/8 or *(2+2+3)/8.

*Treat the numbers as if they were the amount of 8th notes present.
In regards to the mixed meter vs. additive depend:

It depends on the feel of the music.

For example.

9/8 can have three equal pulses. If thats the case it is similar to 3/4, but there are 3 8th notes instead of 2.

9/8 can also have 4 pulses as described above. They simply will not be equal pulses.

The musical content/context are the determining factor, not just the numbers in the time signature.

9/8