Brian,
Am I right in saying that an app like this is a completely different concept to what we have on a keyboard?
On a keyboard/organ these days they take digital 'samples' of various instruments (or for an organ it would be digital samples of 'real' organs eg Wurlitzer, Hammond, Salisbury Cathedral etc.) and this is what you hear when you choose a 'Voice'. And they are getting better at doing this. None of these instruments have the same 'sound' when played higher up or lower down, and that in itself is a challenge to replicate.
On the other hand, with the Syntronic you have access to a base of 17 different synthesizers they have 'sampled' for creating sounds. This is what they say about the Syntronic:
Capturing Synthesizer DNA
When it comes to accurately reproducing the sound of timeless machines like Moog, Oberheim, Sequential Circuits, ARP, Roland and Yamaha vintage synthesizers, sampling their sound-generating oscillators is the only way to ensure truly authentic sounds. We selected some of the most sought after synthesizers, sourced only the best instruments from private collections, and painstakingly sampled them. Sound designers worked hand in hand with software developers to take full advantage of this “synthesizer DNA,” with the goal of offering a highly flexible instrument that would maintain the exact sonic character of the originals while extending their creative potential even further. We have captured multiple round robins of single oscillators, oscillator combinations (including sync and FM sweeps) and after more than 70,000 samples and 50GB later, Syntronik is ready to set a new standard in the world of virtual instruments.
Sounds like fun if you are into creating sounds for your music.
Hugh