Subsections

Emulating plucked instruments: Plectrum Tracks

PLECTRUM^11.1tracks are designed to let MMA create tracks that sound, remarkably, like real, strummed instruments (guitars, mandolins, banjos, etc).

As mentioned earlier in this document, the biggest difference between PLECTRUM and other tracks is that a duration is not used. This means that each string (note) in PLECTRUM patterns continue to sound until they are changed (a new note) or muted.

When creating a PLECTRUM pattern or sequence you simply set an offset, strum duration and volumes for each string of the “instrument”.

To aid in debugging, a special DEBUG option PLECTRUM is provided. When enabled this will display chord shapes for generated chords. See here for information to enable/disable this option.

Tuning

By default the PLECTRUM tracks are set to a standard guitar. However, it's very easy to change with with the TUNING command. This command requires a note setting for each string in the instrument. For example, to duplicate the default:

Plectrum Tuning e- a- d g b e+

In this case we have set six strings. The first string is a low “e”, the second a low “a”, etc.

Similarly, you could define a tenor banjo with:

Plectrum Tuning g- d a e+

Only one TUNING setting can be set for a sequence. It applies to all bars in the current sequence. It is saved and restored in GROOVEs.

If you change the TUNING for a PLECTRUM track after setting a SEQUENCE you must ensure that the number of strings in the PATTERN and TUNING are the same. A mismatch will generate an error. However, setting a different TUNING with the same number of strings is just fine.

Capo

A “capo” is small bar which is placed on the neck of a guitar, banjo or other stringed instrument to raise its pitch. They are quite useful when a song is in a pitch too low for a singer ... a capo placed on the guitar raises the pitch of each played chord. Much easier for a player than having to change (raise) each chord in the song. In MMA the use of a PLECTRUM CAPO setting is a bit different: it doesn't change the chord pitches. A “C Major” chord remains a “C Major” chord. However, the actual note assignments to the different strings on the instrument can (and most likely) changes. Depending on the tuning of the “instrument” a “C” chord with a CAPO 2 will be created as a “B” chord shape played above the second fret. In most cases a chord with a positive CAPO value will have a higher tonality.

To change the CAPO value:

Plectrum Capo 2

In addition to raising the pitch of the instrument, you can use negative values ... in a real instrument you would need to stretch the neck for similar results! There are no limits on the capo values. Very high or low values will have no different effect over moderate ones since the generated notes will always be in the MIDI range of 0 to 127.

Only one CAPO setting can be set for a sequence. It applies to all bars in the current sequence. It is saved and restored in GROOVEs.

It is also possible to change the pitch or tonality for individual chords with the “barre” chord name extension (detailed here).

Yet another way to change the pitch is to use the OCTAVE settings here.

Remember: unlike a real instrument, neither CAPO or barre chords change the pitch (transpose) the chord in MMA . The same chord is played, but with a higher tonality.

Patterns

Setting a pattern for a PLECTRUM track is similar to that of other tracks: you simply set the offset and volumes for the different strings. In addition you must specify a “strum”^11.2 value (used as a delay between strings). The formal definition for a PLECTRUM pattern is:

Offset Strum Strings:Velocity [...Strings:Velocity]

where:

Offset: A beat or offset into the bar. This is used in the same manner as in all the other MMA patterns.
Strum: The strumming delay between hitting each string. Use a positive number for a downward strum and negative number for an upward strum and use zero for all the notes to be played together. “3” is a fast downward strum and “-10” is a slow upward strum.
Strings: The string or strings that are to be plucked. Details below.
Velocity: The MIDI velocity (loudness) for each string. “127” is the maximum volume, A value of zero is used to mute the string or strings. Guitarists often mute the strings with the side of their hand when strumming.^11.3

For a basic strumming guitar you might use:^11.4

Begin Plectrum-Strumming
  Voice NylonGuitar
  Volume m
  Sequence 1.0 +5 120 120 120 120 120 100; \
    2.0 +5 90 80 80 80 80 80;\
    2.5 -5 - - 50 50 50 50;\
    3.0 +5 90 80 80 80 80 80;\
    3.5 -5 - - 50 50 50 50;\
    4.0 +5 90 80 80 80 80 80;\
    4.5 -5 - - 50 50 50 50;
End

This gives eight strums per bar. Note the strum values at beats 2.5, 3.5 and 4.5: using a negative strum value causes the strum to run in the opposite (high to low) direction.

Also, notice the use of “-” values for certain strings. A “-” lets that string continue to vibrate until the next pattern. If you want to disable (mute) a string use a “0” for the volume.

Another example shows how to set up a finger picking pattern:

Begin Plectrum-FingerPicking
  Voice NylonGuitar
  Volume m
  Sequence 1.0 0 - 100 - - 90 -;\
    1.5 0 - - - 90 - -;\
    2.0 0 - - 90 - 90 -;\
    2.5 0 - - - 90 - -;\
    3.0 0 - - - - - 90;\
    3.5 0 - - - - 90 -;\
    4.0 0 - - - 90 - -;\
    4.5 0 - - 90 - - -;
End

To make creation of volume tables a bit easier, you can shorten the notation by setting a range and volume. This is done by using “n-m:v” where n is the start string number and m is the end string number and v is the volume. Please note that the strings are numbered in “reverse” order, just like a guitar. The last string (the bottom and usually the highest pitch) is string “1”, the first string (assuming 6 strings) is “6”. So,

“1.0 0 2:50” is the same as “1.0 0 - - - - 50 -”
“1.0 -5 2-4:80” is the same as “1.0 -5 - - 80 80 80 -”

It is not possible to mix range and individual string settings. So, you cannot do:

“1.0 0 2:50 90” $\includegraphics[height=3ex]{stop.eps}$

Missing volume settings are expanded just like in CHORD tracks. So, assuming a 6 string guitar:

“1.0 0 90 ” is the same as “1.0 0 90 90 90 90 90 90”

However, do note that you must specify either one or all the strings if you are not using a range. Again, you cannot do:

“1. 0 80 90” $\includegraphics[height=3ex]{stop.eps}$

Please note that the following options have no effect in a PLECTRUM track: ARTICULATE, VOICING, STRUM MALLET and DIRECTION.

Footnotes

...PLECTRUM ^11.1: The concept and code base for the Plectrum track was developed by Louis James Barman <louisjbarman at googlemail dot com>. Send compliments to him!
... “strum”^11.2: A “PLECTRUM STRUM” setting is ignored by these tracks. Strum must be set as part of the pattern.
... strumming.^11.3: The PLECTRUM track differs from other MMA tracks as the duration of each note is not given but instead like a real guitar the note on the string will continue to sound until either it is muted by using a velocity of zero or until another note is played on the same string.
... use:^11.4: These examples use BEGIN/END shorthand notation. This is explained in the “Begin/End Block” chapter here.

bob 2010-11-07