The_Complete_Idiot%27s_Guide_To_Music_Theory

Time Signature Beats per Measure
Warning
Don’t assume that an eighth-note time signature is automatically twice as
fast as a quarter-note time signature. Although this might be true (and almost
always is true when time signatures change in the middle of a song), the speed
of the beat (what musicians call tempo) is independent of the time signature.
Thus, a song in 3/8 time actually could be played slower than a song in 3/4.
(Learn more about tempo in Chapter 7.)
Half Time
If you move the other direction from the basic quarter-note time signature, you
get into time signatures based on a half-note beat. In a half-note time signature,
each half note gets one beat; quarter notes get half a beat, and eighth notes get
a quarter of a beat. Whole notes, on the other hand, get just two beats. (It’s not
really that confusing; it’s just more math to deal with.)
Half-note beats—2/2, 3/2, and the like—are typically used in classical music for
slower, more sweeping passages.
The following table presents the most common half-note beats.
Half-Note Time Signatures
Time Signature Beats per Measure
Chapter 6: Time Signatures 71