You have probably heard that effect that DJs' get when they gate , turn on and off , a break beat or vocal or whatever. It's a good effect and usually one that is easy to emulate using Midi. More up to date samplers and synths can have their volume controlled simply using Midi controller 7. The Mirage , however , will not respond to this controller message so I set about looking for a work around.
There is a nice parameter for each of the 4 programs in the Mirage called Mix Mode - Parameter 28. It's a little weird to explain and requires some explanation of the Mirage's Voicing.
First up , when you play a note on the Mirage you are in fact activating two sounds. What you here is determined ,in part, by Mix Mode status. Lets just say we have 2 waveforms loaded into the Mirage and they are waves 1 and 2 ( param 26 ). Wave 1 has a Top Key ( param 72 ) of 15 and wave 2 has a Top Key of 31.
When Mix Mode is OFF you will hear wave 1 and a copy of itself on all the notes up to Key 15 and wave 2 and a copy of itself on all the notes from Key 16 to Key 31. This setting is useful for creating "chorused" sounds by Detuning the copy ( or as Ensoniq call it oscillator 2 ) using Parameter 33 and mixing the sounds using the Oscillator Mix ( param 34 ) and Oscillator Mix Velocity Sensitivity ( param 35 ). If you had 8 waves loaded and Mix Mode was OFF the waves would be arranged like this :
| OSC 1 | - | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| OSC 2 | - | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
When Mix Mode is ON you will hear a mix of wave 1 and 2 depending on certain parameters. What has happened is the Mirage assigns wave 2 to be oscillator 2. If you had 8 waves loaded and Mix Mode was ON the waves would be arranged like this :
| OSC 1 | - | 1 | 3 | 5 | 7 |
| OSC 2 | - | 2 | 4 | 6 | 8 |
This kind of arrangement would traditionally be used for loud and soft versions of acoustic instruments. An important thing to remember with Mix Mode on is that a lot of the wave parameters like Tuning , Relevant Filter Frequency and most importantly Top Key is that the settings for waves 2, 4 , 6 and 8 will not have any effect.
To create the gating or sometimes known as transformer switching effect on the Mirage we need to follow several steps. The first thing to do would be to find and load the sound to be used. It doesn't matter if it almost fills the entire memory , just make sure there is a couple of blank bytes at the end say FE- FF. OK lets say we have wave 1 starting ( param 60 ) at 00 and ending ( param 61 )at FD. Select wave 2 and set it's start to FE and it's end to FF. It's really important that there be no sound in wave 2 for this to work. Now we are ready to turn Mix Mode ON. Next set the Balance ( param 34 ) to 00 as we want to hear wave 1. Finally set the Balance Velocity Sensitivity ( param 35 ) to 00. This is done because we don't want to use velocity to swap between wave 1 ,containing the sound , and wave 2 with only silence. You cant send a velocity message by itself as it is part of a Midi note message. Send a note and you will re-trigger the sound. We want to change the volume of the sound while it is sustaining. With the Mix Velocity Sensitivity set to 00 the mixing is controlled by the Modulation Wheel. Modulation controllers are easy to send from any sequencer and while a note is sustained so it works a treat.
So now we have a sound that will disappear as you push the Modulation wheel. It can be faded in and out quite easily but really fast gating , or switching , takes some pretty active flicking. To get a really neat and clean effect you need to use a sequencer. If a Modulation controller message is sent with a value of 0 then the mix will be all wave 1. If a Modulation controller message is sent with a value of 127 then the mix will be all wave 2 - the silent or null wave. By arranging alternating valued Mod messages you can create rhythmic gating effects.
One way I have used to make it a bit easier is to tap in a rhythmic pattern from a keyboard , on a single note. I then line up Modulation controller messages with both the beginning and end of the notes I have played. From there it's just a matter of setting the values at the beginning of the notes to 0 and the values at the end of the notes to 127. Erase the notes themselves and start playing the sequence. Hold down a key on the Mirage , or send it one long sustained note , and you have a nice rhythmic gate.
Here is a Midi File containing a Modulation cotroller gate to download and examine.
There is a new parameter that can be used under Mirage OS 3.2 to control the Mix Modulator Source , parameter 79. Parameter 35 must still be set to 00 for these to work. I have layed out the values and what they correspond to below.
| Value | Controller | Controller Number |
| 0 | No external controller | |
| 1 | Modulation Wheel | 1 |
| 2 | Breath Control | 2 |
| 3 | Controller 3 | 3 |
| 4 | Foot Pedal | 4 |
| 5 | Portamento Time | 5 |
| 6 | Data Entry Slider | 6 |
| 7 | Volume | 7 |
| 8 | After Touch | |
| 9 | After Touch Polyphonic |
Now you now all you need to get your Mirage gating. It's just up to you to find the right kind of sounds to use. Have fun and don't forget to save what you do to disk !
12 Feb 1998
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