dexed: A Tour of the User Interface

Let’s take a walk around dexed in the “dealer showroom”, shall we? The dexed User Interface, or UI as we’ll call it going forward, can be a jumble of knobs, graphic envelopes, symbols, and keyboard keys when you first open it, but it’s laid out quite efficiently and logically. The layout helps quickly make subtle or grand changes to a sound, or select new ones. We’ll start our overview of the UI with the simple and somewhat obvious stuff first, then move on to the more complex sections.


First, an obvious one – the keyboard at the bottom of the UI. The functionality should be straightforward here and it is – playing a note on the keyboard generates sound in the dexed FM synthesizer engine. There are a couple of interesting details to note, however. First, the position of your cursor on the keyboard generates different velocities in the synth – moving your mouse pointer to the top of the key sends a lower velocity value, the closer to the bottom, the higher the velocity.  Second, when you have a MIDI controller connected to dexed, notes played on the controller are reflected on this graphic by turning a yellow/green color. This can occasionally be a handy debug feature when you need it and offers some “eye candy” along the way.

The next section is the CART / PARM / INIT section on the left just above the keyboard. The “CART” section we’ve already visited in detail in our post about how to get new sounds into dexed. The PARM button, which stands for “Parameters”, has several global parameters for the synth, including Pitch Bend Range, Step, the ability to hide or show the Keyboard, the global Modulation Matrix, and more.  We’ll dedicate a post to this section in the coming weeks – there’s a lot to unravel here. INIT creates an Initialized Patch in dexed. To the right of the INIT button is a pop-up menu that allows you to select a sound from the currently loaded CART, and the STORE button takes you to a dialog for storing copies or any changes to the currently loaded sound.


Directly above the sound selection pop-up are the global Level, Transpose, and a Monophonic / Polyphonic switch. The Global Level is essentially the Master Volume control for dexed, and the Transpose knob adjusts the semi-tone offset for the synthesizer by +/- 24 steps. The Monophonic switch converts a 16-note polyphony dexed synthesizer to a 1-note polyphony synth, stacking all the oscillators on that one note for very fat sounds. While the Level control and the Monophonic switch are not stored within a preset, the Transpose position is.


Two more sections with the “Globals” area if you will are the Tune / Cutoff / Reso section and the Active Parameter display. The Tune knob allows you to make fine-tune adjustments to the synthesizer in cents (I think, as there is no feedback given here). The Cutoff and Reso parameters adjust the Oberheim-modeled, unique to the dexed (and not in the original DX7) low-pass filter. These two parameters are easily my first “go-to” adjustments when loading new Carts of sounds – combining the FM synthesis of dexed with an Obie low-pass is a powerful combination.


In this section, there is also a virtual display below the dexed logo is a reflection of the current edit going on – whether in the Global section or elsewhere on the UI.


Moving along the bottom of the UI just above the keyboard, we come to the Algorithm selection and Feedback programming section. There are 32 algorithms available in dexed, just as there were in the original DX7. Algorithms are the root of sound in the DX7 – each algorithm graphic representation shows how the dexed / DX7 oscillators interact to make sound. The Feedback control is programmable between values of 1 and 7, and for this overview, is an extra timbral control for each algorithm.


Next up is the LFO section. The DX7 has a single LFO per preset, with waveform shape selection, speed, delay, Pitch Modulation (PMD) and Amplitude Modulation (AMD) amounts, Pitch Mod Sensitivity, and Sync parameters for the keyboard. This last parameter resets the LFO to its waveform start point when a key is pressed, otherwise, they run free.


The Pitch Envelope Generator (EG) is the final section along the bottom of the UI in dexed. This is a full-blown EG, in DX7 terms, and is a preset level EG, meaning it affects *all* operators in total, not individual operators within a patch. The EGs in dexed and the DX7 are essentially the same as in subtractive, analog synthesizer, but the parameters are different. This is likely why programming FM is more difficult to understand because it breaks the tradition of “Envelope Time” and replaces it with “Envelope Rate”. In more traditional EGs, for example, on a Prophet 5, as you turn the knob affecting Attack Time to the right, you increase the time it takes for the EG to transition from zero to the programmed maximum. In dexed, turning the knob for EG Rate 1 to the right increases the Rate, which mathematically is the inverse of Time, and speeds the transition between zero and the programmed EG level. So, it’s really just “opposite world”,  and one needs to keep this in mind while programming FM synths.


The final, most complex section of the dexed UI is the Operator (or Oscillator) section of the panel. While it is complicated, we should keep in mind that it is 6 sections, each representing an Operator in the same way. So, if we get a handle on the parameters for one Operator, we can apply the same knowledge to the others.  Each of the 6 operators in dexed has an “on/off” switch that is not labeled but is located to the left of the large, white operator number in each section. Each operator has an octave (Tune), Coarse, and Fine-tune adjustment, and a switch to determine if the frequency is fixed, or if it is ratio relative to the other operators. Each has its very own amplitude EG, and setting relative to how its level is adjusted by the AMod (amplitude modulators set at the global level), and key velocity. Each operator has its own level adjustment, too. The EG can be adjusted by an offset on either side of a keyboard breakpoint and the rates can be scaled against four curves on either side of that breakpoint. Suffice it to say, there is a lot of functionality to get your head around in the Operator section of FM synthesis. There’s also a ton to learn about how each of these six operators interact with each other to perform the wildly dynamic FM synthesis that we all know. Most of this will be studied in greater detail in later posts.

FM synthesis, as embodied in dexed and other FM synths is a deep source of new and different sounds, and understanding the parameters available to you is the starting point for a journey of creating your own sounds. The tour that we just took is not meant to be a meaningful FM synthesis tutorial, but an overview of the knobs and settings that are available in dexed. As we work together over the coming weeks, we’ll understand how each parameter and each section of the dexed UI plays a part in crafting sounds – both modifying existing sounds and creating new ones from scratch.  We’ll put dexed up on jacks and have a look at the Global section and the Operators, and learn how the Operators interact to make those classic DX sounds. Stay tuned! 

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