Tempo refers to the speed at which a song is playing. It represents the time interval between beats in a song and is measured in beats per minute (BPM). Tempo is used by Transitions DJ to synchronize playback between songs.
When you add songs to the library, Transitions DJ will analyze the song and try to automatically determine the correct tempo and the beat locations in the song. The analyzer works well for songs recorded using an electronic clock to keep the rhythm, such as electronic and hiphop, but not for genres such as rock where the there are variations in the tempo.
Transitions DJ has several functions for manually changing the tempo when automatic BPM detection fails. The simplest way to correct the tempo is to use the BPM tap function. The BPM tap function will allow you to tap along with the beat of the music using the mouse and will reanalyze the song based on the taps. The BPM tap function will only work for songs will with a constant tempo.
For songs with multiple or variable tempos, the beat grid must be edited manually. The beat grid editing mode is available for adding and editing an unlimited number of different tempos, allowing complex time warping of the musical signal.
The BPM tap function allows you to specify the tempo of a song by tapping along with the music using the mouse. To specify the BPM using the tap function:
The beat grid is represented by the gray lines in the waveform view. You may have to zoom in before the lines become visible. When zoomed far out, the beat lines are not drawn. As you move in, gray lines will first appear representing the bar or measure boundaries. A measure boundary marks the location of the first beat of the measure, also called the downbeat. If you zoom in enough, lines representing individual beats will become visible, with the downbeats now drawn using thicker lines.
Holding down the ALT key will enter beat grid editing mode. You can tell you are in beat grid editing mode when the beat grid is highlighted. You may also notice the appearance of one or more triangular shaped markers along the top of the grid. These markers represent anchor beats which can be moved to alter the alignment of the beat grid.
In some cases, the Transitions DJ analyzer may misalign the beat grid. Often, the beats are aligned correctly, but the bar boundaries do not align with the downbeats. To shift the beat grid, hold down ALT to enter tempo editing mode and use the mouse to drag the strip above the waveform. This is the region containing the phrase annotation labels. The mouse cursor will change to a hand when moved over the region. You can also shift the tempo grid by pressing ALT in combination with the left and right arrow keys. Each key press shifts the beat grid one-half beat. Alternatively, shifting is available using the menu commands Shift Left and Shift Right in the Tempo menu.
Transitions DJ provides a couple of methods for changing the BPM in case the tempo analyzer detected the incorrect BPM. Much of the time, the BPM is detected incorrectly by a factor of 2, such as 70 BPM instead of 140 BPM. In this special case, you may use the keyboard shortcuts ALT-Up and ALT-Down to double or halve the BPM, respectively. These shortcuts are also available using the commands Double BPM and Halve BPM in the Tempo menu.
In cases where the BPM is not off by a factor of two, you will need to enter beat grid editing mode and manually edit the tempo. The BPM can be altered by expanding and contracting the beat grid.
A general strategy for matching the beat grid to the beats uses a combination of shifting the beat grid and changing the BPM.