Kifele wrote:If I understand it in a good way it means that I could take my watch and measure it by counting
Yes that's right.
Music for aerobics will generally have a strong beat, making it easy to count.
60 x (number of beats counted)/(time) = BPM
Example:
if you count 60 beats in 30 seconds, then the BPM is:
60 x 60/30 = 120 BPM
If you want to increase the BPM from 120 to 140, then;
(% speed increase) = 100 x {(required BPM) - (original BPM)} / (original BPM)
= 100 x (140-120)/120
= 100 x 20/120
= 16.666666666667
The easy way to do this in Audacity is to enter the "From" and "To" figures and let Audacity work out the %
The precision is to 3 decimal places, which I can guarantee is sufficiently accurate. The difference between increasing the speed by 16.666% and increasing the speed by 16.667% is so small that even a trained dancer or musician will not be able to tell the difference (less than 1 millisecond per minute).
To aid counting beats, a lot of music will group beats in 4's (this is known as 4/4 time). Such music can be counted in the following fashion:
1,2,3,4 -
2,2,3,4 -
3,2,3,4 -
4,2,3,4 -
5,2,3,4 -
6,2,3,4 ......
The number that is marked in bold indicates the number of musical "bars", and if there are 4 beats to each bar, then the number of beats = the number of bars x 4.
I have done a lot of work with dancers and they are notorious for changing their mind about what tempo they want a piece of music. They will say "I want it at 160 BMP", so you make it at exactly 160 BPM, and then when they come to putting their movement to the music they say "it's too fast" or "it's too slow".
One way is to work closely with the dancer, and be prepared to change it.... possibly several times.
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