This response, about envelope generators etc, might get a bit theoretical and philosophical, be warned...
About EGs in Yamaha FM synths - agreed, this is a strong point, something that I loved and love about using these instruments. From my point of view, however, what the FreqBox and other MFs allow for is a different paradigm. The EG paradigm, established long ago in the first instruments by Bob Moog and other designers, is event-based - you trigger the EGs, somehow tell a bunch of oscillators what frequency and waveform they're supposed to put out (via CVs in analogue systems), and you get what you've programmed. An almost universal embodiment of this paradigm in the electronic world is MIDI, where the fundamental message form (note on message) represents a single event. This is a perfectly valid way of working, as decades of great music attest. But it's not the only way. Of musical interest is a paradigm of continuous control (and I don't mean MIDI CC messages) - where the control signal varies from moment to moment under direct influence of the performer. In the world of acoustic instruments, a representation of this paradigm is what happens in a woodwind instrument, where the player's breath continuously generates and controls the sound (hey, I'm a shakuhachi player by profession...
). In the electronic world, we have things like pre-MIDI electronic wind instruments where the breath pressure generates a continuous CV, which can be used to control a VCF, VCA etc. But in the electronic world, perhaps the purest representation of this paradigm is the theremin, in which there is continuous bodily contol of two parameters (pitch, volume), and in the Moog incarnations (EW with hotrodding, EW+ , EWpro) we have access to two continuously varying CVs for these parameters (plus gate on the EW+), which can be sent to control whatever we want on our MoogerFoogers, analogue synths or whatever. The point I'm making here is that devices like the MFs, and in this case the FreqBox, allow for implementations of a level of control which is not possible in the digital world. With the FreqBox, we lose the complexity of Yamaha's algorithms and EGs, but gain the possibility of non-quantized continuous control via CVs. (Even using MIDI CC messages to control timbre etc of an FM synth, you don't really have continuous control. The messages are quantized in time - how many messages can flow down a MIDI cable per second? - and in level - 128 steps from 0 to maximum. This is inherent in the digital paradigm - you will always have some form of time and level quantization.) While I still work with the digital paradigm, I'm extremely glad that instruments such as the FreqBox, EWPro etc have come along, as they give access to a performative world of electronic sound at a level of immediacy which is, I feel, missing from the event-based paradigm which underlies the Yamaha instruments (and many others).
Please note, I'm not trying to start an analogue-versus-digital debate focussing on FM, I'm simply presenting my sense of what is so great about the analogue implementations of a particular performing paradigm in the electronic world. Just offering some food for thought...
Comments, anyone?
Cheers,
JimF