Standardized American Style dancing defines the tempo of the music for each particular dance. For example: Foxtrot is 28 to 30 mpm (measures per minute). In standardized dancing, the patterns are designed for the specified tempos. Standardization is needed in competitions so fair judgments can be made. The more standardization, the less subjectivity on the part of the judges.
A somewhat confusing part of ballroom dancing is something called "speed". For example: Two couples are dancing around the floor to music played at a tempo of 30 mpm. A new dancer is watching the dancers trying to figure out how fast to dance. After watching intently for a while, he realizes that both couples are dancing perfectly to the music even though one of the couples passes the other at least twice during a 3 minute song. How is this possible?
Most people think of speed (in relation to dancing) as how fast the music is being played. So logically, you would think that the music controls how fast the dancers move. There is another factor in addition to the music that has an even bigger influence on the movement of the dancers.
First of all, let's define the two terms "tempo" and "speed". "Tempo" is defined as how fast the music is being played (ex: 30 mpm or 120 bpm (beats per minute) in 4/4 time). "Speed" is defined as how fast the dancers physically move across the floor (ex: feet per minute).
Dancing is moving to the music. It is generally the dancer's steps (weight changes) in relation to the beat of the music. If couple 1 takes a step to each beat of music at 120 bpm (30 mpm) and each step is one foot long, they will travel at the rate of 120 feet per minute. Now if couple 2 does the same but takes a step two feet long, they will travel 240 feet per minute. Bottom line, both couples are taking 120 steps (which keeps them in time with the music) but because couple 2's steps are twice the length they will travel twice as fast. The "speed" of the movement is dependent on the "tempo" of the music and even more importantly, the size of the dancer's steps.
Which dance has the fastest "tempo", a 30 mpm Waltz or a 30 mpm Foxtrot? The Waltz is 3/4 time, so 3 x 30 = 90 bpm (.66 of a second per beat). The Foxtrot is 4/4 time, so 4 x 30 = 120 bpm (.5 second per beat). The Foxtrot has the faster tempo even though the mpm's are the same.
Many dancers make the mistake of assuming that strict tempo music means that each step feels the same from a speed point of view. Let's talk about Waltz. The general foot work for Waltz is: heel, toe, toe. When executing a forward heel step, the foot moves from under the body forward to accomplish a weight change in one beat of music. Rise on the second step is created by the toe foot work allowing leg swing. When executing the third step, (toe), the leg starts swinging from behind the body, swings past the body forward for a weight change on one beat of music. The heel step travels half as far as the leg swing step but in the same amount of time (one beat). It is obvious the heel step feels slower than the leg swing step because it travels half as far. It is very important that the dancer understands the fundamental physics and geometry of the four legged animal (partnership) and it's relationship to the music and movement. There can't be any assumptions made, you must understand how it works logically to develop the best and correct feeling for the specific dance.
This is why I say over and over again: "You cannot watch and try to imitate, you must "know" what you are doing." Everything in ballroom dancing is very logical once you understand what is to be accomplished and how it is to be executed.