The Roland D-70 is a 76 key synth first released in 1990 and touted as a "Super LA" synthesizer and successor to the popular D-50. On the contrary, the D-70 is really a sample playback synth and more closely related to the U-20 than the D-50. The D-70 has 30 note polyphony and is five part multitimbral with a dedicated percussion channel. Each patch is comprised of four PCM tones with multimode filtering per tone. If you're counting, that is 20 different waveforms available for playback at any given time, not counting the extremely flexible percussion section.
The D-70 is still my all-time favorite "pry it out of my cold dead hands" digital synth. No other synth I've come across can generate such cold aliasing sounds, which can then be filtered by a very warm non-digital sounding multimode filter. The unit features a great semi-weighted 76 key keyboard with aftertouch, a huge 320x80 backlit display, four assignable faders next to the display, and a second assignable fader by the pitch bend section.
Many users are perplexed by the D-70's rather poor user interface, but once accustomed to it the flexibility is unmatched. The unit features the ability to split or layer the four tones that comprise a patch. At the same time, four zones can be split or layered via MIDI. Any patch can be played locally at the same time as external MIDIed synths without tying up a MIDI channel. Flexibility does not come without a price, and it's easy to forget which split/layer is being edited. Setting up split or zone points is as easy as holding down the corresponding zone button, and pressing the bottom and top key of the zone. Voila! This is excellent for real-time performance. Zone transposition and volume can also be modified instantly with the four assignable faders.
The voice architecture begins with a tone. A tone consists of a sampled waveform or cyclic loop, filter, digitally controlled amplifier, and LFO. The waveform, either internal or from one of the two card slots, can be modified by a process called Differential Loop Modulation. In a nutshell, it takes a small chunk of the sample and loops it. The beginning and end points are user defined, but as they are rather arbitrary, it isn't as flexible as it sounds. Each tone also has its own pitch envelope. Next comes a great sounding multimode filter. Velocity can be routed to filter cutoff, although not resonance. I guess you can't have everything. Same old same old for the DCA section with obligatory envelope. The LFO section IS something I need to mention. No, it doesn't have any great modulation routings. What is DOES do is slow down when you play a big chord. It's not that big a deal, and it is probably useful in some contexts, but it does give some insight to how slow the processor is, specially in regards to dense parts.
A patch is made up of four tones which can be split, layered, or velocity-switched. The ability to stack four tones in a patch is nothing new, but the provision for offsets of tuning, attack, release, resonance, filter cutoff, volume, pan, effects, and output assignment is. This allows more tones to stored in memory because minor edits do not need to be saved in a separate RAM locations.
I purchased my D-70 summer of '95, shortly before selling off my U-20. I loved the U-20's sounds, but was limited by its lack of editing facilities. The D-70 has been great, and after selling off the U-20, only cost me a difference of $250. There are lots of great tricks for milking new sounds out of the D-70, but if I were to detail them all here, would give away my trademark sound.
Now for those sounds. The following sounds are atypical D70 patches created by none other than yours truely. Each patch utilizes only a single osc, however each example has several notes played at once, a pseudo-chord if you will. Each track was played soley from the keyboard, and without tweaking even a single slider over the course of the take. No, this is not CSound. And no, I'm not kidding. This is D70. Hear it roar.

D70 Patch Example 1
D70 Patch Example 2
D70 Patch Example 3

Final Experiment [This track was created completely on the D70 by bouncing live tracks between two DAT machines - a great example of what it can do.]