A soft-split. That indeed would be a nice feature.

The new Nord Stage 3 has it: Split Point Crossfade functionality.

The Motif engine (on which the MONTAGE is based) has always offered some simple and some sophisticated methods "so that as you move up the keyboard the notes gradually fade out". And as we'll see below, before there was sample synthesis, FM has always had a method to do so...

Let's start with AWM2 (Sample based) PARTs first.

Press [EDIT]
Press [PART SELECT 1] to view Part Edit parameters
Touch "Elem1" to view Element 1 parameters
Touch "Amplitude" > "Level/Pan"
Here you can, around the Center point of C3, tilt the "LEVEL/KEY" toward a negative value to decrease the overall output level above middle C. This is your simple/general crossfade parameter... used to simply scale the effectiveness of an Element as you reach the outer edges of the scale.

(Above) As you change the "LEVEL/KEY" parameter to a negative value you are lowering the output of the upper range of keys. This is on a per ELEMENT basis within the PART.

Drop down a level, touch "Amp EG" where you can scale the envelope - in most acoustic situations the higher the pitch the faster the envelope, so this too, can be scaled... very important when doing acoustic emulation to have the response adjust as well.

(Above) Changing the "TIME/KEY" parameter can adjust the speed of attack, for example, so that you can have lower notes attack more slowly or faster than higher notes... Adjust to taste...You can move the CENTER KEY to further define the response. For your particular example, this may not be necessary but is there for detailing.

Finally, touch "Scale" to define four BreakPoints along the keyboard scale so you can radically or subtly adjust the output of the Element across the entire range of MIDI. Here you can set any four points along the Elements region and fashion whatever you might need from gradual to more abrupt changes in output level across the keys. Work with it - it is almost self-explanatory to work with...

The way I want to us this is to layer a piano and bass sound - the piano the entire range of the keyboard, the bass in the lower but it fades out as I head towards middle c (for example) rather than it sounding in full on the note before and then the sound disappearing on the note above.

Make sense?

Sure. Totally possible - should take you a minute to setup with the info above. If you get stuck post back here.

On an FM-X sound, naturally, the method is a little bit different. In FM-X only the Carriers are heard - but you can "scale" the output of each Operator. And as you might anticipate, if you know just a little bit about FM, adjusting the OUTPUT LEVEL of an Operator acting as a MODULATOR will affect the timbre/tone of the sound, while adjust the OUTPUT LEVEL of an Operator acting as a CARRIER will affect the overall volume of the sound. So if you want to change the character of the tone across the keys - this is how it is done... this type of scaling has been available on FM synthesis since the very beginning. (Necessarily, because unlike analog synthesizer where, generally, you use a LPF on everything so high frequency content is rarely an issue with analog synth sounds. However, in FM you are constructing and causing some outrageous high frequency content that often need to be attenuated without killing all high frequency content...) Timbre "Scaling" to the rescue.

Press [EDIT]
Press [PART SELECT (fm)] select an FM-X Part
Touch OP1 to advance to the Operator level of editing... looking at the Algorithm chart determine which Operators are MODULATORS (stacked) and which are CARRIERS (along the bottom of the chart)... remember you can only hear the Modulator through its affect on the Carrier it is modifying. So in general, isolate and scale your Carriers, first, then add each Modulator, in turn and adjust it as necessary.

After determining the role of each Operator you can begin to affect how its level changes left to right across the keyboard
Touch "Level"
You will be working with "Curve Lo", "Lvl/Key Lo", "Curve Hi" and "Lvl/Key Hi".

FM uses the LINEAR and EXPONENTIAL CURVE parameters along with the "Lvl/Key Lo" and "Lvl/Key Hi" parameters to define the scaling response to output level across the keyboard...

To fade a bass out as you go up the keyboard you would select a "Curve Hi" for the Carrier(s) that used a Negative (Linear or Exponential) Curve. Set the "Lvl/Key Hi" = to a value that fades the sound out by the point you need it to disappear. Use a -Linear or -Exponential to have it fade at the rate you desire.

A +Linear or +Exponential Curve will increase the Output Level
A -Linear or -Exponential Curve will decrease the Output level
Lvl Key Lo and Hi work so that 0 is no change and 99 is maximum change.

Wow, thank you Phil.
Montage really is a great machine.
Even the limits do not exist......

Thanks BM - that's answered a lot of my questions too, in a completely unrelated field ...