Triggers

It is possible to have MMA sequences to be automatically played only when certain conditions apply. This is controlled by a TRIGGER.

TRIGGERs are available for all tracks with the exception of MELODY and SOLO. TRIGGERs are not saved in GROOVES.26.1

Once you understand the concept of a TRIGGER, we think you'll find them very useful. Suppose, for example, that you only want a chord to be played on a track when the chord changes. First of all you need to create a chord track:

Begin Chord-1
   Voice Piano1
   Octave 5
   Sequence {1 1 90 * 4} // chords on 1,2,3 and 4
End

If you used this with the following data:

1 C / D
2 C Gm

you will get chords sounding on each beat in the bar.

To enable a trigger to only sound when the chord changes:

Chord-1 Trigger Auto

Now, the chord will sound on beats 1 and 3 of the first bar and 1 and 2 of the second.

With that under our belts, let's have a look at all options available:

First, commands which do not require an additional option:

Auto
This keyword signals that a trigger should occur at any point when a chord is changed. In this case you do not need (nor should you have) a BEATS option. Note: For this command and REST the actual point for the trigger is the exact point of the chord/rest change (this could be at an offset like 1.1415).

Off
Turns the trigger for the specified track off. This is the same as having a TRIGGER command with no arguments. No other commands are permitted with an ``off'' setting.

Rest
This keyword signals that a trigger should occur at any point where a rest starts. In this way you can handle a rest like a ``special'' chord.

The following commands are set in the OPTION=VALUE format:

Beats
A comma separated list of beats for your trigger. Note that this is ignored if you have set one of the keywords AUTO or REST. The beats can be any legal offset into the bar (in 4/4 this would include 1, 2.4 and even 3.9).

Bars
The bars of the sequence to apply the trigger to. For example (assuming a four bar sequence):

Chord-1 Trigger Auto Bars=1,3

would limit the sequence to chord changes occurring in the first and third (of four) bars of each sequence in the song.

Cnames
A list of chord names which are checked against the active chord at each point of the BEATS list. Example:

Chord-Test Trigger Beats=1,2,3,4 Cnames=Cm,E7,FM7

If the chord name is not in the specified list, no trigger is activated.

Ctonics
A list of base chord names which are checked against the active chord at each point of the BEATS list. Example:

Chord-Test Trigger Beats=1,2,3,4 Ctonics= C,E,F

If the tonic of the chord is not in the specified list, no trigger is activated.

CTypes
A list of chord types (e.g., ``m'', ``7'', ``dim'') which are checked against the active chord at each point of theBEATS list. Example:

Chord-Test Trigger Beats=1,2,3,4 Ctypes=m,m7,dim7

If the chord-type is not in the specified list, no trigger is activated.

Count
The number of patterns to use from the sequence. If you have a sequence of four events (like the example at the start of this section) only the first event is used. However, by setting the count to a value:

Chord-1 Trigger Auto Count=2

more of the patterns will be used. No pattern will start past the end of the current bar. The above example doesn't really make a lot of sense, but with a sequence like:

Chord-1 Sequence {1 3 90; 1.3 3 90; 1.6 3 90}

and a COUNT of 3 you can have a triplet play for each trigger point.

Measures
You can limit the trigger events to specific measures. For example:

Chord-1 Trigger Auto Measures=1,5,9

will cause trigger events to be played only when a chord changes in bars 1, 5 or 9.26.2 Please note that the bar numbers are not checked against the actual bar numbers in your song (which can be hard to calculate after repeats and endings), but with the number label in the file. So a trigger command in the above example will apply to all of the following bars, regardless of the order of the numbering:

5 Cm
1 G
1 D
5 E7
9 A

Please don't number your bars like this! It's just an example.

Override
By default, when a bar is parsed and the trigger command does not create any events MMA will generate an empty bar for the track. However, by setting OVERRIDE=TRUE the original sequence for the track will be used. Use of this command (in conjunction with the SEQUENCE command) lets you have different patterns for bars with and without a trigger response.

Sequence
By default, a TRIGGER will use the SEQUENCE defined for the track. This command defines a different sequence to use. This can be useful in toggling between the track sequence and the trigger's by turning the trigger on and off. Define the sequence in the normal manner:

Chord-1 Trigger Auto Sequence = {1 3 90; 1.33 3 80; 1.66 3 70}

Only one sequence is permitted in a trigger command.

Sticky
This is a convience option to set the STICKY bit for the current track. Its effect is the same as described here. When using the option in a TRIGGER line you must include the ``='' as in:
Drum-Triangle Trigger Sticky=True

Truncate
The duration of the notes in the sequence used by a trigger are, normally, left as defined. If you are using short notes, this works just fine. But, if the durations are longer you can end up with overlapping notes. The TRUNCATE command forces MMA to truncate the duration of each note to the lesser of what is specifed, the start of the next pattern or the end of the current bar.

Things to note:

A number of example files are included in the distribution in the directory egs/trigger.



Footnotes

...GROOVES.26.1
If triggers were part of a groove, the triggers a user creates would disappear on a groove change. Probably not what is expected.
... 9.26.2
This is a good reason to number each bar in your song, as recommended here.
Bob van der Poel 2017-03-25