Tempo & Rhythm

Music tends to have a steady tempo to it, often measured in "beats per minute". A simple observation is that most music is in the range of 50-200 beats per minute, the same as the extreme range of our heartbeats. In general too, the tempo of a piece of music roughly equates with the heartbeat associated with the corresponding physical state or emotion which the music suggests.
Anything in the range 60-80 beats per minute is calm and relaxed, less than 60 is often very relaxed, introspective or even depressed. 80-100 is moderately alert and interested. 100 upwards is increasingly lively, excited or agitated and, since we crave some degree of excitement from our entertainment, 80-120 is quite a common tempo, and even 120-160 is common in some energetic situations. We're not saying that there is an absolute correspondence between heartbeat and music tempo, but there is a strong degree of suggestion between the two. Music moves in time and suggests movement, and we tend to associate music unconsciously with movements made by our bodies while talking, walking, running, dancing, riding, etc.
To illustrate this, note that marches are in duple time (2/4 or 4/4 ) giving that "left, ..., left, ..., left, right, left, ..." feel. In contrast to this 3/4 time seems to completely lack that left-right feel, and we therefore frequently associate it with circular motions, like swirling waltzes, or roundabouts at the fun-fair. Music suggesting a horse galloping or a train ride is fast with more complicated rhythms representing 4 legs or several sets of wheels.
This latter example illustrates that while tempo sets the basic pace of music, there are many ways in which composers can alter and adjust this using different note patterns or rhythms. Syncopation is a familiar example with notes unexpectedly landing "off the beat", which adds complexity and interest to a basic beat, often turning a simple march tempo into a jaunty swagger (see Ragtime). The rhythm of music can qualify the repetitive nature of the underlying beat by suggesting more or less frequent movement. Even though the tempo of a piece of music might be slow and relaxed, a high frequency of notes can suggest a degree of contained excitement within that relaxed state. But the combination of Tempo and Rhythm has an immediate almost physical impact on our perceptions.