Dotted whole notes
A dotted whole note equals 6 beats,but it all depends what time signature you playing a dotted whole note in. In a 6/4 time signature a dotted whole note would equal 6 beats. But in a time signature with the denominator of 8 the value of a dotted note changes.
In a time signature with the denominator of 8 every note goes up by half. For example, in 6/8 an eighth note, which equals half of a beat, equals one beat in a 6/8 time signature or any other time signature with the denominator of 8. A quarter note equals 1 beat in a 4/4 or 2/4 or any other time signature with a denominator of 4. But in a denominator of 8 time signature, a quarter note equals two beats, because it goes up by half of its value. So where would you use a dotted whole note in 6/8 time signature? You can't, because the change in the value of the dotted whole note won't be able to equal out the number of beats in a 6/8 time signature. So it's best to use a dotted whole note in 12/8 time signature, because a dotted whole note would equal 12 beats in a time signature with the denominator of 8. If you are confused about how music notation works, then I'd suggest that a good foundation needs to be laid out about music notation and reading theory. Some good links would be musicresources.com, pianonanny.com, or try googling and searching for some good music theory websites.