I’m sorry for this looooooong post. But I had too much spare time and thought that I could try to explain some of the previous ideas and a few new ideas more into details.
I’ll try to explain the concept of multi-instruments together with something I call ‘Instrument-Patterns’ in a common and a more technically way.
So dont worry if this is confusing at first read 
Its suppose to be easy on top, and more complex and flexible if you dig into it.
Picture 1
Picture 2
Edit: Picture 3
Multi-instruments:
Now… As most trackers know (or should know). Multilayering of instruments that play the same notes might be just what you need to make a sound more phat, deep, special, ‘pro’, good, whatever 
Most synths use two or more wave generators to form the sound. Many new ones use up to 6.
Some combine this with samples.
Ok, point taken. It would be damn useful if you could trigger multible instruments at once in renoise. Some people would say that you loose control this way. You CAN do multilayering by just copy/paste a track and change the instrument in one of the tracks. Others will say that copy/pasting is not innovative or inspiring. I would say there is a time for both. It would be a damn hassle if you had to track each wavegenerator (osc) for each synth you inserted. Kills your inspiration. However. After/during the composing, you might wanna go into more details.
So why not have both things?
In the first picture you can see that you are in the advanced tab in Instrument Editor.
On top left you can enable Multi-instrument. Now if you take a look in the instrument list, you will se that there is a + sign when Multi-Instrument is enabled. Open it and you will get a - - - empty - - slot.
Here you can insert another instrument (vsti or sample), and the - - - emtpy - - - slot will go one step down so you can add another one etc.
This is the most basic use of multi-instruments. Hitting a note will trigger all the instruments inside the multi-instrument equally. Should be very useful in its simple way of use.
Later I’ll tell how ‘instrument-patterns’ and ‘scaling’ can change the multilayering concept into an even more dynamic and flexible synth/sampler.
Instrument level fx:
On the right side of the picture you can see a Instrument-pattern. (more about the Instrument-Pattern later)
Even if the Instrument-patterns are not activated, you can still use the two tracks all the way to the right ( I Mst and I S00). They are ‘Instrument master tracks’. If you put any fx on the ‘I Mst’ it will affect the entire instrument.
If you look at the renoise internal DSP chain you will realize that from the moment you put any fx into the Instrument tracks (I mst) then your instrument will behave like a vsti (only one stream out).
You have to use this instrument in one track only. This is also true if your Multi-Instrument contains one or more vsti.
Now… as discussed in another thread. This might be too limiting for some. It IS possible to duplicate everything for each polyphony. But it CAN be very cpu intensive. But not always.
So maybe you should be able to set a ‘True Polyphony’. Where the default poly is 1.
The ‘Voices’ setting I have included in the picture was just ment as normal polyphony. Just as you set in any vsti. A true polyphony will have multible streams out of the instrument.
However this is not an issue if you only use samples in your Multi-Instrument (and non instrument-level fx’s)
This is also one of the reasons I would wish for a ‘render instrument’ feature. (explained later)
Renoise will then render out each note and velocity layer into another instrument with only samples.
Instrument-Patterns:
Now we are getting into more advanced stuff.
The idea is that you have a pattern with its own notes, fx and instruments for each note and velocity layer in your instrument. If you for instance press a c-4 on your midi keyboard with a velocity of 30, then the pattern that has that range will be played.
(see first picture) Over the pattern you can see its range. note = C-4 and velocity = 30-40.
You have another pattern for note: C-4 velocity: 20, and another one for D#4 40 etc etc.
You can decide the resolution and the bounderies for your velocity layers in the keyzone window. Theoretically you can have 10(octaves)*12(notes)*127(velocity layers) = 15240 patterns.
But its nuts to use all the velocity layers. And you dont need 10 octaves either. A more typically scenario could be to use 4 octaves and 4 layers. = 192 patterns.
As you can guess there is no limit to what you can do with a pattern
Automate, commands, use multisamples/instruments. Play a seqeunce/arpeggio etc. You simply cant get more flexebility then this. You can now for instance treat each sample in your instrument as a instrument it self (adding envelopes/filter etc).
I also included a sustain/loop function in the pattern. Have a look at the line numbers in the pattern. There you can adjust this. The green part is the release part of the pattern.
So in this example you can see there is a release sample (C-5 82 on track 02). Release samples are very often used in GIGA, Kontakt and other big formats.
You can also synch the Instrument-Pattern BPM to the song BPM.
If you enable Instrument-Patterns you will se that in the instrument list you will get another [+] sign.
(Picture 2)
Open it and you will see all the Notes used in the instrument. You can then open each Note to see the velocity layers and finally the list of instruments/samples used for this single pattern only.
However. Very often you wanna use the same instrument in several patterns (for instance you usually dont wanna load a string or bass vsti for each single Instrument-pattern when you are gonna use the same instrument over several Instrument-patterns). So I suggest that the first 80 (hex) instrument slots are dedicated to what I call ‘common-instruments’. You load the common-instrument just like you load the Multi-Instrument. It will be on top of the list under the [+]MultiInstrument. In other words, if you wanna load a instrument/sample that you are gonna use in ONE pattern only, then you have to browse to that pattern in the instrument list. Press the [+] and you will get a - - -empty - - - slot (that will have an instrument number 80 or higher). This way you wont get a conflict with the Common-instrument numbers (slot 00 to 80).
((You cant just have Common-Instruments as its limited to FF(hex) slots. Even if you had FFF slots they will not be sorted that good. So it will be damn hard to find the right sample/instrument. So thats why each single Instrument-Pattern has its own unique 80-FF slots.
This also gives more room for instruments without increasing instrumnet-number-digits in a pattern. A GIGA file can easily contain several thousands samples. If that many samples was to be loaded as single common-instruments in Intstrument-Patterns, then you would need more digits))
Speaking of the Instrument list… might be a good idea to be able to expand the list like on the second picture. Should be plenty of room if you use somehing higher then 1024* resolution. Also a small button on the bottom of the instrument frame to expand/shrink the list. The expansion could also work in smaller resolutions when you are in Pattern Editor. When you go into other middle-views it could auto-shrink the list.
Or ultimately you could undock the list to a separate window. Why not make the entire tracker dockable?
My dual monitor setup would really like that.
There will also be room for other lists like clip/pattern/RAM-samples/FX tabed into the bigger list.
Even customizable tabs to sort instruments into groups.
Back to the edititng part of Instrument-Patterns:
You can see that you have different modes of editing the patterns. Edit All means of course that you edit all patterns at once. If you type anything in one pattern it will be the same in all others.
The exception is if you have ‘Auto Note’ enabled. This means that if you for instance type in the note F-4 in pattern C-4 , then in pattern D-4 the note will be autoadjusted to G-4 etc. So you dont have to go into each Instrument-Pattern and change manually to get the right pitch.
Edit single, will edit only the pattern you see.
Edit selection means that you edit a selected range of patterns. You select this range on the scale-keyboard or select a group of patterns in the keyzone window.
Edit note means that you edit all velocity layers in the current pattern note.
ADSR:
I also think you should be able to choose which type of envelope setting to use on instrument Amp and Filter in the Instrument Editor.
Drawing envelope points are very cool but also very static. Its not that efficient if you gonna automate or scale the envelopes.
We would need an option to choose either normal envelopes drawn by envelope points, or ADSR and cutoff, reso and env amount.
You can hardly find any synth or sampler that do not have ADSR/cut/reso/amount… and for a good reason.
There are several ways to implant this. Just have a look at different envelopes in vsti’s like rhino2 (which has both types), fm7 and pro53 to see what I mean.
Scaling:
(see first picture)
Scaling is one of the key features of any synth to make instruments sound real and dynamic. It makes it much easier to vary the sound and ‘live feeling’ when you play on the keyboard. It can be essential to program good instruments.
There are lots of things you can scale here.
As you see on the x-axis you can scale over the keys or the velocity.
If you choose velocity you will scale between the velocities from whitin the note range you have selected on the keyboard.
On the y-axis you can have all kind of things.
Some universal, and some only for the Instrument-Patterns.
First you can have a per instrument midi in <–> velocity-out scaling.
This will scale the velocity on your midi input keyboard.
You can also scale the velocity of each instrument in a Multi-Instrument (common-instruments).
If you have a multisample instrument made of samples, then you can scale the volume of the instrument (not the same as velocity).
If the instrument is not a common-instrument or if it is just made of samples then you can freely scale the panning too.
If you have ADSR enabled for an instrument (amp and/or filter), then you can scale each parameter here.
And of course you can scale Cutoff, Reso and Env Amount. (You know… Hitting the keys light will have different cutoff then hitting the keys hard etc)
Now if you enable ‘Instrument-Patterns’ you can scale alle the fx paramters you have used over several zones.
In Unisone mode (polyphony=1) you can scale even single inserted fx.
In the first picture you can see that the Compressor ratio is scaled for the velocity on the note c-4.
In this case that means that if you hit the key c-4 softly, it will compress with ha higher ratio then if you hit the key c-4 heavy. Can be very handy if you program drum banks etc.
Now there are issues with this. If you have a technical view of the DSP routing you will see that you will need a unique compressor on each velocity layer. So you can end up using quite a lot ram/cpu on this. But this is totally up to the creator of the instrument.
However, if the instrument is unisone (polyphony 1) then only one compressor needs to be used.
Anyway… you can do lots of lots of things with fx scaling.
If you for instance put a reverb on the ‘I s01’ (instrument master send channel). And then put a send device in all the Instrument-Patterns, then you can scale the amount of reverb you want on different keys or velcities.
As you are scaling a send device you will only process one reverb.
If you got the ram and cpu, and the plugin support it, then you can also put a unique reverb on each Instrument-Pattern. This will make you able to scale all the reverb fx parameters. Like the lenght of the reverb (hitting a key hard can make the reverb longer then hitting it soft. Or C-5 will have more early reflection then C-4 etc etc).
The possibilities are endless. And its all up to the programmer of the instrument to choose how heavy on the cpu it will be (In the year 2010 with 8 multi cpu cores this might not be a problem 
).
And also. You choose how many Instrument-Patterns to use. (the resolution of velocity layers and note range)
But a huge warning should appear every time you are about to insert a fx/vsti into multible patterns at once.
Instrument Presets:
I think you need instrument presets(programs) if you are gonna import other formats like AKAI/GIGA etc.
It would be nice if the .rni had its own internal bank. So if you make large and complicated instruments you should be able to make several programs. I guess this belongs somewhere in the ‘Instr.Settings’ tab. Maybe a ‘Multi-Instrument Properties’ like you have ‘Midi Properties’ , ‘Sample Properties’ and ‘Vsti Properties’?
Keyzones:
Ok. I did not make a picture of the keyzones. You all should know how it works. Have a look in other vsti samplers.
There is one difference though. You should be able to swtich between two windows. One where you are inserting samples directly into zones. And another window where you insert Instrument-Patterns.
I agree with It-Alien in the first post in this thread. A list of all samples/(Instrument-Patterns) used in a selected key would be very nice. With boxes to type values.
Oh…One more thing here could be to have resolution presets. Simply a set of presets to set up the zones.
Instrument rendering
Finally as you have made that kick ass instrument, you just realize that it uses 70% of your cpu 
And you might not be as free as if it was a pure samplebased instrument (has to do with internal DSP routing and polyphony). You can smell the limits in the same way that vsti’s has limits.
Then you could render your heavy instrument into a simple samplebased instrument.
You know what I mean if you have seen the Arguru/discoDSP vsti HighLife or if you have rendered vsti’s into samples/sf2 using Chainer.
You can set up instruments of vsti’s and add fx (vst) as you wish, and then render it out to samples…
You choose the note lenght, the release lenght and the note-range and how many velocitylayers it will render out. Hit render and you are free.
One nice trick would then be to render out the same instrument several times.
First you turn off all fx like reverb/chorus/delays etc and render out the dry instrument. Then you render out 100% wet reverb,and then 100%chorus etc. Then you could set up the new instruments into a new Multi-Instrument. Then you can easily adjust/scale the amount of reverb/chorus you want. And its all sample based, thus not using much cpu. The reverb you can easily change the lengt (shorten the tail) by just adding envelopes to the samples and fade out etc etc.
Some other examples of use:
If a vsti plugin is not too heavy on your cpu you could insert several plugins to get better control of each note. Almost like samples. Lets say you insert the Vsti pro53 on slot 00 (common-instrument). You find a cool setting. For instance a bass sound. You set voices in pro53 to 1. Turn of fx you dont need. Now its pretty easy on the cpu. Then duplicate this instrument over to slot 01 to 0F. You now have 16 instances of the same pro53 plugin. You can then insert them into different Instrument-Patterns. For instance you set instrument 00 on F-2 and all patterns(notes) below.
Then you can set 01 on G-2, 02 on G#2, 03 on A-2 … … 0F on G#3 and all above.
You can then pan each note almost as you like. Use different commands on them that will only affect that single note. Almost like samples.
Ok I’ll stop now… now Taktik can come and say that nothing of this is possible to make, and its just too complicated and confusing
I’m just trying to generate ideas
cheers
-pysj
), I will explain what Lxx did:
