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Alesis Andromeda - how to implement polyphonic aftertouch
Old 19th September 2011
  #1
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Alesis Andromeda - how to implement polyphonic aftertouch

I have found a way to implement polyphonic aftertouch on the Alesis Andromeda using a MIDI controller with monophonic aftertouch.

You need a MIDI controller with mono aftertouch and the ability to transmit in MIDI Mode 4. MIDI Mode 4 is an accumulative monophonic mode, which means the MIDI controller will send key 1 on MIDI channel (n), key 2 on MIDI channel (n+1), key 3 on MIDI channel (n+2), etc. Your controller may have an option for number of MIDI channels in Mode 4, IE you can specify an upper limit of channel 8 so that other devices on channel 9 and up are not affected.

Say your Andromeda MIDI base channel under the Globals menu is channel 1. You want channel (n) on the MIDI controller to be channel #1. Under this configuration when you press keys and engage the aftertouch, your MIDI controller should send note on and mono aftertouch messages on MIDI channel 1 for key #1, the next key will be MIDI channel 2, the next key will be MIDI channel 3, etc. Every key will have its independent MIDI channel and mono aftertouch - an alternate poly aftertouch.

Configure a patch on the Andromeda that uses MIDI Aftertouch to modulate something - like the filter cutoff. MIDI controller mono aftertouch is equal to "MIDI Aftertouch" in the Andromeda modulation source list.

The Andromeda does not appear to have a MIDI Mode 4 so we need to configure a mix setup on the Andromeda with (n) layers, every layer playing the aforementioned patch. Layer one is assigned MIDI channel n, layer 2 = MIDI channel n+1, layer 3 = MIDI channel n+2, etc.

Unfortunately for Kurzweil MIDIBoard owners, there is a bug in the firmware in that all mono aftertouch messages are only transmitted on the first MIDI channel ([email protected]!). Another MIDI controller may operate correctly.

But I did prove this concept by multitracking MIDI tracks on my seqeuncer using my MIDIBoard on different MIDI channels - and this works!
Old 19th September 2011
  #2
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crufty's Avatar
Genius!!!
Old 19th September 2011
  #3
Oli
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This would work with multi tracking but live there would still only be one value of aftertouch transmitted at any one time.

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Old 19th September 2011
  #4
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Mardi Gras's Avatar
 

I don't understand what aftertouch is... Even after reading into it lol
Old 19th September 2011
  #5
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Quote:
Originally Posted by Oli View Post
This would work with multi tracking but live there would still only be one value of aftertouch transmitted at any one time.

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It can be done live with the right controller. Read it again.
Old 19th September 2011
  #6
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dougt's Avatar
 

Hmm guess we should ask for MIDI mode 4 in the next Chroma CC+ update...
Old 19th September 2011
  #7
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Quote:
Originally Posted by Mardi Gras View Post
I don't understand what aftertouch is... Even after reading into it lol
basically = pressure exerted upon keyboard keys

The harder you press, the higher the MIDI aftertouch value gets generated

This can be mapped to for example a filter to open and close it, ie, make the sound go brighter & duller by varying the amount of pressure you exert on the keys
Old 19th September 2011
  #8
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Hmm guess we should ask for MIDI mode 4 in the next Chroma CC+ update...
Old 19th September 2011
  #9
Oli
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Quote:
Originally Posted by The Real MC View Post
...using a MIDI controller with monophonic aftertouch.
Quote:
Originally Posted by The Real MC View Post
It can be done live with the right controller. Read it again.
Doesn't the monophonic aftertouch imply that there is only one value transmitted at any one time, even if it can be transmitted to separate channels concurrently? I believe that is how my keyboards behave.
Old 19th September 2011
  #10
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Quote:
Originally Posted by asbak View Post
basically = pressure exerted upon keyboard keys

The harder you press, the higher the MIDI aftertouch value gets generated

This can be mapped to for example a filter to open and close it, ie, make the sound go brighter & duller by varying the amount of pressure you exert on the keys
so its like velocity but after the keys have been pushed down?
Old 19th September 2011
  #11
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Quote:
Originally Posted by Mardi Gras View Post
so its like velocity but after the keys have been pushed down?
Well sort of - Like velocity, it does involve how you play the keys. But there are important differences.

1. Midi velocity creates a "value" or data message based on how fast a key moved from 'not pressed' to 'pressed' at the start of the note. This data can be used to do things like increase attack time, set the filter cutoff higher or whatever. However, it is just a static value, a non-changing number between "0" and "127" depending on how fast you pressed the key at the start of the note. This number is different for each key press, of course, but once it is created for a given key press it does not change as the note sustains.

2. midi aftertouch is created by gradually pressing harder or lighter on a key, not faster like velocity. It is more like operating a mod wheel - it can CHANGE as you gradually press harder and lighter on a key. So you can use it to gradually open and close a filter, gradually increase and decrease vibrato depth etc.

Using BOTH of these parameters to affect different things in the same patch can add a ton of expressive control to your playing, but of course you need to practice your keyboard skills to make the best use of them.
Old 19th September 2011
  #12
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Quote:
Originally Posted by Mardi Gras View Post
so its like velocity but after the keys have been pushed down?
yeah you could look at it that way...

for example:

keys already down.... sustaining a chord, press harder and filter opens, release pressure filter closes whilst sustaining

(of course you don't have to map it to the filter but this is a common use for it)
Old 19th September 2011
  #13
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Mefistophelees's Avatar
Quote:
Originally Posted by The Real MC View Post
I have found a way to implement polyphonic aftertouch on the Alesis Andromeda using a MIDI controller with monophonic aftertouch.
So I'm guessing a keyboard that supports polyphonic aftertouch and MIDI mode 4 should allow you to do this live.

It should thus work with the Roland A800 Pro I was looking at...

Anyone got one of those and a Andromeda to try?
Old 19th September 2011
  #14
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so once again Andromeda FTW....always FTW - why even be suprised at this point.

I gotta get a cheap controller and try this out - how long did it take you to work this out?
Old 19th September 2011
  #15
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Quote:
Originally Posted by Mefistophelees View Post
So I'm guessing a keyboard that supports polyphonic aftertouch and MIDI mode 4 should allow you to do this live.
correct

Quote:
It should thus work with the Roland A800 Pro I was looking at...

Anyone got one of those and a Andromeda to try?
There's gotta be something out there that works...

Quote:
Originally Posted by Zombie H View Post
I gotta get a cheap controller and try this out - how long did it take you to work this out?
Not long. Having some sort of MIDI monitor to see the data coming out of the controller did help. The idea came to me from a GS thread a week ago when we were talking about MIDI modes, then <slap> why didn't I think of that sooner
Old 19th September 2011
  #16
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Quote:
Originally Posted by Oli View Post
Doesn't the monophonic aftertouch imply that there is only one value transmitted at any one time, even if it can be transmitted to separate channels concurrently? I believe that is how my keyboards behave.
No.

Monophonic aftertouch is per MIDI channel.

MIDI provides 16 independent MIDI channels, so you can have 16 independent monophonic aftertouch messages per channel.

Think of MIDI Mode 4 as the voice assignment system in analog polyphonics. Key 1 triggers voice 1, key 2 triggers voice 2, key 3 triggers voice 3, etc. Replace "voice" with "MIDI channel" and that's how MIDI Mode 4 works.
Old 19th September 2011
  #17
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Unfortunately Im not a keys player by trade, and complex MIDI setups give me the heebie-jeebies, so I cant get too excited. But its nice to know I guess. How much does this change the potential of the keyboard, and how often would you realistically use poly aftertouch in making a patch?
Old 19th September 2011
  #18
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Quote:
Originally Posted by cdog View Post
How much does this change the potential of the keyboard, and how often would you realistically use poly aftertouch in making a patch?
Oh judas. On an analog polysynth the possibilities are insane.

Filter sweeps, hard sync sweeps, pulse width, waveshaping, cross mod, mix levels, mod wheel, pitch bend, oscillator bend (think ring mod or hard sync), volume swells (brass stabs), fading in and out elements of a sequence, LFO frequency modulation (press harder=faster LFO), sweeping pads or strings or choir voices in and out...
Old 19th September 2011
  #19
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Quote:
Originally Posted by The Real MC View Post
Not long. Having some sort of MIDI monitor to see the data coming out of the controller did help. The idea came to me from a GS thread a week ago when we were talking about MIDI modes, then <slap> why didn't I think of that sooner
very very cool idea tho - can you post a recording of it using an A6 Patch?

Old 20th September 2011
  #20
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Quote:
Originally Posted by The Real MC View Post
No.

Monophonic aftertouch is per MIDI channel.

MIDI provides 16 independent MIDI channels, so you can have 16 independent monophonic aftertouch messages per channel.

Think of MIDI Mode 4 as the voice assignment system in analog polyphonics. Key 1 triggers voice 1, key 2 triggers voice 2, key 3 triggers voice 3, etc. Replace "voice" with "MIDI channel" and that's how MIDI Mode 4 works.
Wrong. Unless the keyboard mechanism has individual sensors for pressure under EACH KEY, you won't be able to simulate poly touch on the Andromeda or anything else that can receive it. While the trick that the OP described WILL let the Andromeda simulate reception of poly touch, you won't be able to send anything resembling poly touch from an Akai MPK or Novation controller, or any but a very small number of keyboard controllers. Infinite Response VAX77, some Ensoniq TSRs, Yamaha KX, Sequential T8, Kurzweil MIDIboard, and the like. There are very few to choose from.

Keyboard controllers that have mono aftertouch usually use a single sensor under the frame that mounts the keybed mechanism to the case - open up a PPG Wave and check out the teeter-totter scheme they used.

Using the OP's trick with a controller that sends channel aftertouch will still allow for interesting effects, but it won't be any different than playing one sound on one MIDI channel, unless you're drawing individual channel aftertouch curves for each MIDI channel in the edit window of your sequencer. If you do have a keyboard that actually senses and sends poly touch you'd have to remap outgoing poly touch to channel touch if the receiving instrument doesn't expressly receive poly touch, which is a whole 'nother bag of hurt.
Old 20th September 2011
  #21
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Exactly! The reason there are way more mono aftertouch controllers than poly aftertouch ones, with the reason being the cost to implement, is because of the cost of having a sensor per key. The mono ones only have a sensor that's able to emit one value for the enter keybed, whereas the poly ones have a sensor for every key.

By the OP's logic, mono aftertouch keyboards DO have a sensor per key, but they chose to save 5 cents and implement a circuit that's hamstrung by its ability to only send out a single aftertouch value on one channel, and you can circumvent that with his trick. And that's pretty much the most asinine thing imaginable!
Old 20th September 2011
  #22
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Thank you. By all means, everybody, feel free to post an audio demo of aftertouch-controlled filters opening individually for each note when played from a channel-aftertouch controller keyboard in MIDI mode 4. We'll be here waiting...
Old 20th September 2011
  #23
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Yup. I think the cheapest way to do something like this and actually be able to play live with poly AT (rather than recording separate mono parts) would be to find an old Ensoniq VFX or similar, which are some of the few affordable keyboard synths that actually did have the ability to SEND true poly aftertouch, and then route that to the A6 or other synth that has the ability to actually receive true poly aftertouch. I've done this by controlling an Emu Morpheus (which has poly AT receive)with the VFX.
Old 20th September 2011
  #24
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Even on synths that send PolyAT like my Chroma it seems like you would also need to convert the PolyAT messages to MonoAT (they are different MIDI codes)...
Old 20th September 2011
  #25
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Yeah I should have clarified that you need a controller with a polyphonic aftertouch sensor.

It's bedtime now, I'll see about putting up an audio clip tomorrow night.
Old 20th September 2011
  #26
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Also the Prophet-T8 does not send traditional PolyAT. It can only send individual key AT in MIDI Mode 4 (mono).
Old 20th September 2011
  #27
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Quote:
Originally Posted by cdog View Post
Unfortunately Im not a keys player by trade, and complex MIDI setups give me the heebie-jeebies, so I cant get too excited. But its nice to know I guess. How much does this change the potential of the keyboard, and how often would you realistically use poly aftertouch in making a patch?
well... (strictly imo) it's a bit like having a smartphone loaded with a gazillion features which are there but you don't ever end up using....

Don't think too many cats out there actually make use of or have a desperate requirement for poly aftertouch, nice as it may be to have that capability "just in case you may need it some day".

Even mono aftertouch..... it has its uses but (strictly imo again) it can be more of an annoyance than a help.
Old 20th September 2011
  #28
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can I request the Bingo Boys Church patch with poly AT routed to the envelope 2's attack

:headexplodes:
Old 21st September 2011
  #29
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Here is a sound sample of my experiment

I am holding every note from the beginning throughout the whole sequence, using aftertouch to modulate the filters and blend in desired notes.

And in here are the MIDI sequence, A6 patch (#118), and A6 mix (#127) so you can recreate the experiment on your A6. When you play back the sequence, make sure Mix #127 is up. Uses MIDI channels 1 through 8.
Old 21st September 2011
  #30
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Quote:
Here is a sound sample of my experiment
Cool. A magic trick. I love Penn & Teller.

So let me get this straight, you put every voice of your Andromeda on a separate MIDI channel, somehow told your controller (through the mysterious MIDI mode 4) to treat the whole thing like a singe patch. I think you certainly could get the effect, but you would have to make a special multi-mode preset on the Andromeda to comply, along with an equally intricate program for the controller(?). Because it just won't work like that out of the box. You're running it like 16 separate synths in special multi presets you made...

P.S. I never heard of MIDI mode 4. Any one else actually pull this off?
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