I do have a Mk 1 - I love its form factor which is why I decided on the Mk1. Plus the value for money is outrageous
Re file structure, not 100% sure which aspect you’re referring to to be honest.
Sets are a thing of the OT only as far as I know. But the A4, like the OT within sets and the DT at its base is organised in Projects that contain patterns that are organised in banks. So it’s symmetrical in that way.
Another thing the A4 has is “Kits”. You can save individual sounds as presets but then you can also save a combination of presets laid out on its four tracks as “kit.” This way, you can switch between sound sets / preset combinations quite effortlessly. A great feature for performance.
The way I work with my DT, OT and A4 is that I mirror projects on all three devices. Patterns are also laid out symmetrically, so bank 1 pattern 1 on the OT goes with bank 1 pattern 1 on the DT and A4 etc.
What’s neat about the A4 is that you either have four mono synths (each track one voice) or you can use it as four voice poly. Then there’s two oscillators + one sub oscillator + noise generator + AM and FM capabilities + two filters + two envelopes + two LFOs + Overdrive + FX Sends to Reverb, Chorus and Delay…all PER VOICE…it’s a sound designer’s dream! I love designing pads and atmospheric sounds on it and find its sound very emotive, very beautiful.
That said, when I first got it I thought it sucked lol. But that’s because I didn’t spend the time to really dive in and approach the A4 as what it is - instead I treated it like my odd monosynth. For example the filters really work together. Filter one is a Low-Pass Filter and it’s quite “thinning” on its own + I don’t like the sound of its resonance all that much. Ok, but now combine filter one with a Peak filter on filter 2 and sweep the frequency range with that and suddenly it sounds beast! Or for more classical mono synth sounds / filter action, I realised I could skip filter 1 and set filter 2 to low pass, then play with that (different sound). Also Oscillator volumes make a difference on the A4 as well as gently overdriving a voice will change the way the filters sound.
Combine all of this with the ability to sequence and p-lock right there in the machine and you have a total winner.
What I mean to say, for the money a Mk 1 changes hands for these days, you will not find that much synth ANYWHERE. And even at full price, it is a really attractive offering.