The "Time base" dialog

To change the metronome value, type cmd-t. The " Time base " and " Metronome" dialogs are displayed (see Fig.18).

Fig.18 "Time base"and "Metronom" dialogs

There are two ways of adjusting the clock. The " Metronom" dialog deals with conventional metronome settings, i.e. "mm = 400" means 400 ticks per minute. You may change this value, for instance, to 345.08. Changes are reflected in the " Time base " dialog. Now it tells "8627 ticks in 1500 seconds", which actually means the same as "mm = 345.08". If you need to set the time base accurately, type directly the numbers of ticks and/or seconds. Whenever you change values, BP2 finds the simplest integer numbers yielding the expected integer ratio. The "Metronom" dialog may display a rounded value which will not affect accuracy since BP2 actually uses the integer ratio displayed on the "Time base" dialog.

A very accurate clock is needed to superimpose BP2 items on a given (digitized) sound track. In addition, synchronisation tags (see §6.6) or Apple Events (§6.7) make it possible to start items on precise dates determined by the environment.

The "Time base" dialog contains boxes allowing the definition of three independent cycles that produce ticks on marked beats. When "Play ticks" is checked, ticks become audible. Ticks may be mapped to any MIDI key, channel and velocity. For each cycle, first adjust the cycle duration (1 to 40 beats), then check the boxes of all beats that need to be stressed by a tick. Each cycle may run at a speed differing from that of the basic clock if its speed ratio is not 1/1. A typical example is given in the time base saved as "-tb.slowshift" which may be opened (cmd-o) when the "Time base" dialog is in front.

It is possible to define each tick of the time base individually. Click any square of a tick cycle with the 'option' key down to display the " Tick settings " dialog (Fig.19).

Fig.19 "Tick settings" dialog

The ON/OFF button determines whether the beat should be audible. If "Use default settings" is checked then the tick will be heard on the default channel, key and velocity of its cycle. If "Use special settings" is checked, then these parameters are specified individually as shown Fig.19. The "Capture settings" button makes it possible to pick up these parameters from a MIDI device. It's a good idea to send ticks to a MIDI sampler with percussive or fancy sounds.

A tick cycle may be captured as a MIDI stream and pasted to a sound-object prototype (see §2.3.3). Ultimately, if the sound-object is played alone it can further be saved to a MIDI file (see §14.1). This is a good trick to use tick cycles created by BP2 with other MIDI software.

The time base continues ticking, if instructed to do so, while BP2 is improvising items. You may check this with examples contained in "-da.tryTicks". Note that in smooth time (see §9) beats may become irregular, depending on time streaks created by the musical item. Try "-gr.tryTimePatterns" to hear the difference. These superimposed ticks are neither saved in MIDI files nor interpreted as Csound events.

Different settings of the time base have been saved as -tb.<name> files representing the most popular talas of North Indian classical music.

The time base allows an accurate transcription of durations when notes are entered from the MIDI keyboard (typing cmd-j, see §1.5). When "Play ticks" is checked, durations are transcribed following the period notation (see §1.12.1).