The TR-909 sequencer brought a really cool new feature that was missing in the 808 and 606 before it: dynamics. Aside from the global accent, many of the instruments allowed two distinct dynamic levels on each step.
To look at how this worked from a user perspective, first let’s look at the TR-808: if you have a blank pattern and press one of the step (“GP”) buttons, its corresponding LED lights up and you have activated a drum trigger on that step. Press the button again, the LED turns off, and you have turned off the drum trigger on that step. That’s two different states: off and on.
On the TR-909, the beginning is similar: the LED for a given step is off when there is no trigger programmed. Press the GP button for a given step, and the LED comes on, but at 1/2 brightness. You have activated the trigger, and the note will play on that step, at 1/2 dynamics. Press the GP button again, the LED comes on at full brightness, and the step will trigger with full dynamics. The step will turn off when you press the button a third time. That’s three different states: off, half, and full.
There has been some discussion of a hypothetical “MB-9090” in which the MIDIbox 808 software is used to control a 9090 board (from Trevor Page) to make a TR-909 clone. It’s a great idea, except that AFAIK TR-909 dynamics can’t be realized with the current software.
I suspect that modifying the MIDIbox 808 software to allow two different dynamic levels on each step is feasible. But the hardware problem of dimming the LEDs to provide visual feedback of the dynamics per step is a problem - the TR-909 uses PWM to dim the LEDs, and it has been stated elsewhere that 8-bit MIOS can’t do PWM dimming effectively due to the required CPU cycles.
Perhaps a solution to this would be to use 16 additional DOUT pins, which the builder could use to either light the same LEDs at half brightness (via highter-value resistors) or a second set of LEDs to indicate the lower dynamic level per step.
The two-level-dynamic feature would need to be something that can be defined, per instrument, in the setup.asm file. Also, the level would need to affect MIDI velocity, and likely a CV as well.
Anyway, this is just a concept. I’m not (yet) a MIOS programmer so I suggest this capability with all modesty, as right now I do not have a clue where one would even begin to make something like this a reality. But at this point I think it’s important that the idea gets out there, because it is the only thing standing in the way of making the world’s first fully featured TR-909 clone.