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 Forum index » Instruments and Equipment » Sequencers
Sequencer Transpose - How should it work?
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Frank Luchs



Joined: Mar 16, 2007
Posts: 18
Location: Munich

PostPosted: Fri Mar 14, 2008 4:45 pm    Post subject: Sequencer Transpose - How should it work?
Subject description: Discuss how you would like the seq react to your keyboard input
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Sequencers and Arpeggiators might use different ways to react on your musical input. A single note played on the connected MIDI-keyboard might change the sequence immediatly, on the next beat or on the next bar.
The transposition can be made parallel or forced to the current key.
The parallel mode might change the current key, this depends on the programed notes and the pressed note. The forced mode would use the new root and translate all notes to the nearest note of the scale.

Example:
Let us have this motiv: c g e d e f

1. Chromatic Transposition
The most common transpose method is the chromatic transpose:
You play a note on the keyboard and the sequencer plays the motiv using the pressed key as new root. All pitches of the melody are shifted by the same count of semitones. In some cases we might leave the key.

Pressing c: c g e d e f
Pressing g: g d b a b c
Pressing e: e b g# f# g# a
Pressing eb: eb bb g f g ab

As you can see, the motiv is fine for c and g to stay in the same key, but when you press the note e, we can see a change of the key from C-major to E-major. The same happens when playing the note eb, we leave the key, coming to eb-major.

This kind of parallel transposition might be desired, it is often used in sequenced electronic music. Listen to the ZYKLUS Z8 Demo:
http://www.synthware.com/tutorials/Z8/Z8_Demo_Frank_Luchs_VelocityMix03.mp3

2. Scalar Transposition
The other option is the scalar or diatonic transpose, where we use ScaleSteps instead of semitones.

Pressing c: c g e d e f
Pressing g: g d b a b c
Pressing e: e b g f g a
Pressing eb: what to do ? simply ignore this key or force to e?

As you can see, the motiv is the same as in the chromatic transposition for c and g. But when you press the note e, we can see that the system 'thinks' in terms of 'a third above', and uses only intervals from the scale. If we play a note which does not exist in the current scale of the sequencer we have two options:
1. We ignore this note completly, the sequence plays as if there is no input
2. We force the input down? to the next valid semitone, in this case we obtain e.

***
Another thing to discuss is what should happen, if the pattern repeats.
Example: We have 2 alternating melodies.

Melody A, 3 Bars: c==== g=== e= d= e= f=
Melody B, 1 Bar : g==== f=== e==== d====

When you press a new note while the sequencer is playing the melody A, it will take this note as new root and play the melody transposed until the end of bar 3. With g played this results in g==== d=== b= a= b= c=.

Then it will change to melody B. If we have released the keyboard before reaching Bar 4, the melody B will play in the original key starting with note g.

Now Melody A should be played for the second time. We don't press a key on the MIDI-keyboard. Should we now hear the original melody
c==== g=== e= d= e= f=
or should we use the last stored transpose for this part
g==== d=== b= a= b= c= ?

So what do you think? When and how should the system react?
The next discussion will be about polyphonic input.

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bronswerk



Joined: Mar 15, 2008
Posts: 1
Location: netherlands

PostPosted: Sat Mar 15, 2008 4:33 am    Post subject: Reply with quote  Mark this post and the followings unread

Using 1-key input, the chromatic version is in my opinion the best option, because this mode should be available anyway and it's what most people expect. So you don't have any problem when in scalar mode and the user strikes a key out of scale. And once tranposed it stays tranposed until the next input comes by.

All scalar transpositions schemes are only valid when in multiple input mode. When hitting a full chord eg a major triad you can determine the root and scale.
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egw



Joined: Feb 01, 2003
Posts: 1511
Location: Asheville NC
G2 patch files: 8

PostPosted: Sun Mar 16, 2008 7:44 am    Post subject: Reply with quote  Mark this post and the followings unread

Scalar transposition is all you need. Chromatic is the default mode if you allow user defined scales.
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