| What is Tempo?
Tempo is the speed at which the music is played, so it is an important part of a MIDI performance. Indeed, the ability to alter the tempo at any point in a song during both editing and performance contributes directly to the MIDI format's power and flexibility.
What is a "Tempo Map"?
By default, the Tempo View (or tempo map) can be found beneath the Clips View, and to the right of the Metronome View. Here's what it looks like:
The current song position is designated by a vertical red line, just as it is in the Clips View and Piano View. The tempo is represented by a series of lines connected at points called "nodes." Nodes are "tempo objects" and are drawn as red squares, or white when selected.
There are two kinds of tempo changes represented in the tempo map: Step and Slope. Step tempo changes occur when the tempo suddenly changes from one tempo to another. Step tempo changes are drawn as horizontal red lines. Slope tempo changes occur when the tempo gradually changes from one tempo to another over a period of time. Slope tempo changes are drawn as black lines.
Internally, all tempo changes are actually step changes--MIDI Maestro is able to "detect" slopes so that they may be more logically represented, and you may more easily manipulate them. In fact, if you "zoom in" on a slope, you may eventually see the individual steps that comprise the slope.
When the tempo map's y (vertical) axis is completely "zoomed out" (this is the default), the bottom of the map corresponds to the lowest tempo (this may vary according to your screen resolution, but it will be about 2.0), and the top of the map corresponds to the highest tempo (always 350.0).
How is Tempo measured?
By convention among musicians and music software, tempo is always measured in "quarter notes per minute." This is regardless of whether the time signature is common, cut, or 6/8 time. You will see this abbreviated as BPM, that is Beats Per Minute.
What is the Tempo Multiplier?
The current tempo as determined by the tempo map is always displayed in the lower-left hand corner of the Metronome View. In the example below, the tempo playing is 112.3 BPM.
The number to the left of the tempo is the "tempo multiplier," here 1.059. By default, this number is 1.000, but it has a range of 0.500 to 2.000. The tempo multiplier (1.059) is multiplied by the current tempo from the tempo map (106.00) to derive the actual tempo that is used to play the song (112.3).
The vertical slider control that's located to the left of the large beat readout controls the value of the tempo multiplier. You may use the mouse to drag the blue ball up to speed up, or down to slow down.
There are also menu commands for manipulating the tempo multiplier.
How do I change the Tempo?
The simplest way to change the tempo is to use the Insert/Tempo command, which opens the following window:
A simple step tempo change is achieved by entering the new BPM value and pressing Enter. For those interested in knowing how tempos are internally represented in MIDI files, and for those who just can't seem to get enough math, the equivalent microseconds per quarter note value is also shown.
Clicking the mouse button in the "tap box" will automatically set the tempo based on a short-time average of your clicks per second.
Here are some step tempo examples:
If you specify a "through" time, you may also specify a "through" tempo, and several other options become available. Hint: try selecting a range of time before using the Insert/Tempo command.
If you specify two different BPM values, you will create a tempo slope, as shown below. The "return to original value" setting causes the tempo to return to its pre-slope value at the end of the slope.
The above picture shows a "smooth BPM" transition. Some experimentation was done with "smooth usec/quarter note" transitions. The results of this option applied to the above example is shown here:
Under certain circumstances this second type of transition may be more desirable. However, it is more difficult to manipulate in the Tempo View.
By specifying a time range with the same BPM values, you create a step, but additionally, all intermediate tempo changes in the time range are deleted.
Can I graphically "draw" tempo changes instead?
Yes. In the toolbar at the top of the MIDI Maestro window, select the pencil tool. You then have a choice to draw straight lines (to create steps and slopes) or freehand lines (for more exotic tempo maps). Make your choice of line type by clicking the corresponding icon found to the right of the pencil icon.
Now, move the cursor over the Tempo View. You will notice that beneath the Tempo View, the time and tempo corresponding to the cursor's position is displayed. Click and release to create a tempo step. Click and drag the cursor to a new position to draw a line. Notice that when a perfectly horizontal line is achieved, it will be drawn in red. Release the mouse button when the desired line has been drawn.
Once a tempo has been drawn, it may be moved by clicking and dragging the node. Clicking and dragging the node on the right-hand side of a horizontal segment (a red line) moves it independently of the node on the left-hand side, allowing you to create a slope. Clicking and dragging the node on the left-hand side of a horizontal line moves both nodes up and down together.
Can I tap and record a series of tempos?
The Insert/Series of Tempos command does this:
This feature is extremely useful for expressing a rubato or "con moto" section. First, you specify the size of the beat that you will be tapping, then you tap the tempo exactly as it should be played beginning at the current song position.
For every key that you press, MIDI Maestro will created a tempo step. Here're the results from the above example:
The "play MIDI notes" option allows you to hear the music play as you enter the tempo changes. | 
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