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Doctor Jurgenbüster's Casebook

Martin Russ dishes up another concoction of MIDI hints and tips.


Martin Russ dishes up another concoction of MIDI hints and tips.

ALL NOTES OFF!



The following problem has come up so often recently that I have decided to post a warning: beware of keyboards which send an All Notes Off message whenever you stop playing any notes. The reason behind this warning is simple - they can upset the behaviour of expanders, especially piano expanders. But why?

Piano technique is a complex mix of tone and dynamics: the major control of timbre and volume is achieved by the way in which the keys are struck, although additional character is given by the use of the pedals - notably the sustain pedal. Without the judicious use of the sustain pedal, the piano sound loses much of its expressive and emotional strength, and performing some pieces correctly can become difficult if not impossible.

The MIDI controller for Sustain is Controller 64 ($40 in hex code). It sustains or holds all the notes which are being played when it is activated, as well as any new ones which are added subsequently, until the pedal is released. Depending upon the particular sound or implementation, this sustain may be in the form of a decay to the sustain level of the envelope, or may be a slower decay to silence. In normal circumstances, the use of the sustain pedal produces substantially the effect required until the number of notes being sustained exceeds the maximum number of voices available, at which point note-stealing may occur, and the earliest played voices may be re-assigned to new pitches.

Unfortunately, when the sustain pedal and the All Notes Off message meet, there can be confusion. You will find that on some expanders the All Notes Off message will override the sustain pedal, so that when you remove your hands from the keys the sound abruptly stops. For other instruments the note assignment can occur with active voices, causing abrupt clicks and other unpleasant noises, often interpreted as distortion. The Kawai K1 is an example of a keyboard which sends All Notes Off whenever you lift your hands from all the keys, and using this with an expander like the Yamaha EMT10 causes the piano's sustain to become clipped and ineffective, regardless of any use of the sustain pedal.

Even instruments which behave normally in most circumstances can be persuaded to behave badly because of this effect. I have heard of an example where a sampled grand piano exhibited the distortion-type effect because it was used to record a complex piano piece into a sequencer, and was then used as the source of the piano sound for playback. The problem occurred because the original recording was made by playing the parts for the two hands separately, and the resulting performances were merged into the final piece (I must confess that my left hand really does struggle with some pieces, and I have used exactly this two-pass technique to 'cheat'!). The merging thus produced a composite track where the All Notes Off messages were relevant to each hand in isolation - so when one hand was not touching the keyboard, the other could be trying to sustain notes. The end result was a sequencer track which would not work correctly with the same instrument that was used to input the notes in the first place! The solution is to filter out the All Notes Off messages whilst recording or playing back.

The MIDI Specification 1.0 does not seem to prohibit the use of All Notes Off messages to indicate when no keys are pressed - it only says that the message should not be used instead of Note Off or Note On with zero velocity messages. Interestingly enough, the manufacturers whose equipment does send All Notes Off (whenever you are not touching the keyboard) always seem to have expanders which behave correctly when you use the sustain pedal!

My personal interpretation of the purpose behind the All Notes Off message has nothing to do with indicating when no keys are being pressed - I always assumed it was intended to prevent 'hanging' notes when you stop a sequencer in the middle of a note event, or change a track from one channel to another whilst the sequencer is playing. This is the application to which most manufacturers seem to adhere, although even it can be defeated when an instrument does not respond to the All Notes Off message (the DX7 MkI, for example)!

MICHAEL BODDICKER BRASS SOUND



It is the classic programmer's nightmare. You arrive at the studio and the client plays you a track from a CD, and says: "I want that sound." In my case, the sleeve notes gave only the clue that the sound had been programmed by Michael Boddicker, the famous American session synth programmer. The only other assistance I had was my ears - so I listened to the sound, hard!

It was an analogue brass sound, but there was a wonderful 'detuning', 'tearing' sound as the notes started - and I had never heard anything quite like it. It was not the rather cliched pitch envelope detuning found on DX string sounds, nor was it portamento - or was it? A few quick experiments revealed that it was indeed portamento but used in a very different way: Take an analogue brass sound - you really need that VCF sweep sound for the best effect, although an FM brass sound can be used at a pinch. Now double it - and I mean double it, you will need two synths or expanders for this technique. Connect them together as master and slave, via MIDI, and verify that both are playing. (You may detune to taste at this point.) And now for the interesting bit: set up different portamento rates on the two synths - just audible on one, and slightly longer on the other. Now when you play the master synth you should hear the effect I described above - it really is remarkably effective on brass sounds.

As with all the best things in life, you may need to practice in order to get the best out of anything new. In this case, you should experiment to find out how to use the effect for your particular playing style. You may need to adjust the portamento rates to obtain the best impression of dynamic detuning, and it is probably as well to mix the two synths to the same stereo position, rather than spread them out.

MASTER KEYBOARD AS EXPANDER



I have observed several cases recently where problems have arisen because of advances in technology - namely the way that most synthesizers can also be used as master keyboards. More specifically, many people buy DX7IIs or D50s as a master keyboard, and use it to input notes to a computer-based sequencer, which then drives a synth expander. The problems occur when you try to use the sequencer to drive the master keyboard and the expander, as well as try out sounds and ideas on the expander using the same master keyboard. You will find that you need either to have the computer switched on and acting as a MIDI Thru box, or you need to switch the expander input between the master keyboard Out and Thru sockets.

The solution is very simple. Take a MIDI switching unit (such as those sold by Philip Rees) and connect it so that it selects between the Out and the Thru of the master keyboard. You can now use the same setup for trying out sounds on the expander by playing the master keyboard, and for playing back sequences on both the expander and the master keyboard.

Other solutions are possible using master keyboards which have a Local Control Off function, but they have none of the immediacy or simplicity of the above system.

STEINBERG D110 FIX



In his review of the Steinberg D110 Editor in this issue, author David Hughes mentioned that he managed to accidentally erase the contents of the D110's memory by careless use of the Steinberg Editor's send and receive utilities. Fortunately, David found a way to 'fix' this, which is not documented in the D110 manual.

If you switch the D110 off and then, holding the Write/Copy and Edit buttons down, switch the machine back on, the message 'INITIALISE (y/n)' appears in the display window. Pressing the 'up' arrow button will now reset the memory contents to the original factory presets.

Such undocumented features as this are quite common on many devices, and would appear to be part of the 'secret' diagnostic test routines used by service engineers to help repair faulty equipment. If any readers know of similar features, please write and tell us about them.



Previous Article in this issue

DACS MIDI Patchbay

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Software Support


Sound On Sound - Copyright: SOS Publications Ltd.
The contents of this magazine are re-published here with the kind permission of SOS Publications Ltd.

 

Sound On Sound - Mar 1989

Donated & scanned by: Mike Gorman

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Topic:

MIDI


Feature by Martin Russ

Previous article in this issue:

> DACS MIDI Patchbay

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> Software Support


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