I was thinking from a point of view of actually having two pianos in the same room. Two distinct sound sources will always sound more realistic than pre-mixed (just because one's brain expects the room's acoustics to respond differently to two physically separate sources). I like your idea of utilising the capabilities of 5.1 sound card for this.

I've just moved house and we're setting up my partner's piano teaching studio, where we have an acoustic grand, and will also set up a couple of independent Pianoteq / open source organ/synth enabled keyboards. But the setup will be more for piano duets, non-piano instrumental comping and as teaching aid rather than for layering sounds (though no doubt we'll give that a shot too).

As far as latency goes, as long as it's low enough it should not matter. If you have two acoustic grands in the same room, the "latency" or mismatch in times of sound reaching one's ears just from the finite speed of sound in air will typically be of the order of 10 ms depending on where the listener is situated (sound travels about 3 m or 10 feet in that amount of time). With reasonably recent hardware Pianoteq+MIDI latency can be kept to much less than that.

I agree with you though that the simplest setup that does what one's after is always the best.

regarding two computers - personally I think if you've enough CPU it's better to run multiple instances in one computer - otherwise you'd have to multiply the midi output from your master keyboard, and then if the 2 computers have different latency then the models would be out of sync no?

But a simple fun thing is to pan the two (of more) instances of Pianoteq hard left/Right - or you could take things further in a 5:1 system and have four pianos in surround :-)) An autopanner is also fun for the more spatial of you all.

(one of the only parameters I'm surprised Pianoteq doesn't have is a pan or auto pan in the FX module, although it's easy to get around with DAW/Mixers etc)

Edit: Aah, now I've started thinking about the 5:1 surround sound possibilities of the mic placements……. unfortunately I don't have 5:1 in my studio, but I'm playing an arena tour in November with PianoteQ and the PA is vast….. has anyone tried this out? Any feedback would be appreciated.

...ramp down the volume..
Even Ableton Live using Chains within a device rack and velocity fade range, ummm doable!!
Between us; this can spice up next Pianoteq Contest, or not.

Sure - I didn't imagine I was the first to do this :-) But I was surprised that similar piano models 'sang' so well with each other instead of phasing like samples would.
So many possibilities……. yes - your method of ramping the volume range would be another solution I'm sure.
I think Harp & 'sichord might be a fun combination also...

Try the 1922 Erard or the model K with the new model B. 

Lanny

I layered my personal Blüthner program (my favourite model) over the Model B - which has many wonderful qualities also just to see what would happen.

The only range I didn't really like was the extreme low end, where a real piano has only one bass string per note. Despite carefully matching the tuning and intonation the multiple bass strings sounded unnatural. I opted eventually to exclude this key range from the Model B instance (again in Receptor it is simple to define the midi key range for each plugin).

Of course purists might be horrified, but for some it might be a nice tip as each different piano model has different advantages.

:-))) Now I have a "Blütway" and very nice it is too!

Pianoteq is just THE BEST!