Control Soft Knobs with Foot Pedals

The Virus TI's three soft knobs (also known as value knobs) can each be configured to control several parameters to differing degrees and even in different directions, facilitating richness and complexity of timbral variation in real time. But I have found several advantages in controlling (or perhaps emulating is a better word) the soft knobs with foot pedals / expression pedals / control pedals / foot controllers / continuous controllers / whatever-you-want-to-call-them:

• Both hands are free to play the keyboard.
• The feet can easily control two soft knobs simultaneously.
• For even more complexity of timbral variation, one hand can control a knob, such as a third soft knob (value knob), while the feet control up to two soft knobs.

The training video Animating Using Soft Knobs shows in detail how to program the soft knobs. I will just recap the main points that are relevant for foot control.

Within a patch, each soft knob may be assigned to either a parameter or a MIDI control change number (CC#). For foot control, the soft knobs have to be assigned to CC#s. This is because an expression pedal must send the Virus the same CC# as is assigned to the soft knob that the pedal is to control. I will explain how expression pedals can send the Virus CC#s later. In the Virus’s modulation matrix, the CC# assigned to a soft knob is mapped to one or more parameters, specifying the degree, positive or negative (-64 to +63), to which a change in the CC#’s data value (0 to 127) will change each of the mapped parameters.

If a soft knob is currently assigned to a parameter, here is what you need to do to allow foot control while still having the soft knob and its mapped expression pedal control the same parameter:

• In the modulation matrix, configure a CC# for maximum positive control (+63) of the parameter in question.
• Change the soft knob’s assignment from the parameter to the CC#.

This is straightforward for most parameters but can be problematic for some. The names of the parameters that can be assigned to soft knobs are occasionally a bit different from those that can be assigned in the matrix. Usually I can work out the equivalents. But I have found a few parameters that can be assigned to soft knobs but not, so far as I can tell, assigned in the matrix. Analog Boost Int and Unison Spread are examples.

I’m going to assume that it is either difficult or undesirable to change the CC# that each expression pedal sends. That is in fact the case with the rig I’m going to describe later. Assuming then that the CC# sent by each expression pedal is effectively fixed, we need to adopt a standard approach: in each patch for which we want to enable foot control of the soft knobs, the three soft knobs need to be assigned to the same three CC#s.

There is no way of controlling the soft knobs via MIDI that is
a) global rather than patch-specific
and therefore
b) completely separate from the soft knob to matrix linkage and co-existing with it.
If there were, there would be no need map standard CC#s to soft the knobs separately for each individual patch for which foot control is required. In thread MIDI Control of Soft Knobs, I have proposed global MIDI control of soft knobs as a new TIOS feature. If you would find such a new feature useful, you can ‘vote’ for it by adding a post to that thread.

Meanwhile, unless and until global MIDI control of soft knobs becomes available, what are the best three CC#s to assign to the three soft knobs in each patch for which foot control of the soft knobs is required? If you only want to do this with patches you have written yourself from scratch, it does not matter, provided you adopt a consistent approach. But if, like me, you wish to enable foot control of many preset patches and of patches that are modified versions of original presets, I recommend using the following assignments:

• Soft knob 1: CC#1 (Modulation Wheel)
• Soft knob 2: CC#6 (Data Entry)
• Soft knob 3: CC#3 (Control 03)

These are the most commonly assigned in the Virus's preset patches. I estimate that a large minority of the presets come like that. So having the expression pedals send those three CC#s minimizes the work required to tweak the patches to allow the expression pedals to control the soft knobs.

Having explained how to configure Virus patches for foot control of the soft knobs, I shall now show how to make expression pedals send the Virus the required CC#s.

One expression pedal can be plugged into the Virus’s Control (Ctrl) Pedal socket, which can be assigned to the CC# that is in turn assigned to one of the soft knobs. But there are three soft knobs. Two or three (or more) CC#s can input to the Virus via its MIDI In socket. To take advantage of that, we need a method, external to the Virus, of converting the signals of the two or three expression pedals into CC#s which are then merged into a single MIDI cable to be plugged into the Virus’s MIDI In.

There are several devices on the market that can convert an expression pedal’s signal to MIDI. But I have not found anything quite as suitable as the MIDI Solutions Pedal Controller. Compared with the other devices of which I am aware, it has the following advantages for our specific purpose:

• It does not come with built-in footswitches or buttons you don’t need.
• Consequently it is small and very light, though you do need one per pedal.
• It is powered through its MIDI input socket, so there’s no need for a battery or wall wart.

In my rig, I’ve got four expression pedals. Three are plugged into MIDI Solutions Pedal Controllers and one is plugged directly into the Virus via its Control (Ctrl) Pedal socket. I use the one that one is plugged directly into the Virus to control master volume and the other three to control the soft knobs. Obviously you could do with one less expression pedal and one less MIDI Solutions Pedal Controller if you do not want to control volume by foot.

Before the MIDI Solutions Pedal Controllers are connected to the expression pedals and the synth, they first each need to be plugged into a computer, usually via a MIDI-USB adaptor/cable/interface of some sort, to be programmed to convert the expression pedal signal to the required CC# with a range of 0 to 127 (decimal). For details of how to do that, please refer to the instructions that come with the MIDI Solutions Pedal Controller and which are available for download. I will just mention a couple of points.

The MIDI messages output by each MIDI Solutions Pedal Controller need to specify the Virus’s channel number. But you need to subtract one from the channel number to do this. So, if the Virus’s channel number is 1, which it would be by default, you need to specify 0 for the channel number in the MIDI message.

The MIDI Solutions Pedal Controllers will be connected in series to the Virus. So, to allow the MIDI messages from previous pedal controllers in the series to be passed through, MIDI Echo needs to be set to On for all but the first pedal controller in the series.

To prevent the possibility of a MIDI loop, MIDI Echo should be set to Off for the first pedal controller in the series unless you are sure that either
a) there will be no MIDI input to the first pedal controller, in which case it does not matter whether MIDI Echo is On or Off
or
b) you do want to pass through any MIDI input and it will not make a MIDI loop, in which case MIDI Echo should be On.

Once the MIDI Solutions Pedal Controllers have been programmed, they need to be connected to the expression pedals and the Virus. I’m going to assume that
a) no sources other than the pedal controllers need to send MIDI messages to the Virus
and
b) the Virus itself is to provide MIDI power to the pedal controllers.

Obviously one expression pedal is to be connected to each MIDI Solutions Pedal Controller. I have successfully used both the Roland EV-5 pedal, which is not suitable for plugging into the Virus via its Control (Ctrl) Pedal socket, and the Yamaha FC-7 pedal, which is suitable for plugging into the Virus via its Control (Ctrl) Pedal socket. So it seems that the MIDI Solutions Pedal Controllers will work with many, if not all, types of expression pedal.

The MIDI Solutions Pedal Controllers need to be connected in series (MIDI Out to MIDI In) to each other, with MIDI Echo on each pedal controller set as described above and the last pedal controller in the series connected to the Virus’s MIDI In.

Up to four MIDI Solutions devices can be powered in series from a single MIDI source that is capable of providing MIDI power. But they can only receive MIDI power through their MIDI In sockets. So, even though no MIDI messages need to be passed into the first pedal controller in the series, its MIDI In socket still needs to be connected to something to provide power. I connect my first pedal controller to the Virus’s MIDI Thru socket. Connecting to the Virus’s MIDI Out socket works too, though in that case it is essential to have MIDI Echo set to Off for the first pedal controller to avoid a MIDI loop.

Well, there you have it. I hope some Virus players will find this useful. And I would be interested to hear of any variations to the approach described.

Simon

Once everything is set up, you can get a visual check that it is all working by looking at the Easy page of Virus Control. When an expression pedal is moved, so will the indicator on the corresponding soft knob in Virus control. Check that a full sweep of the expression pedal provides full variation of the soft knob. I did once have a faulty pedal that would only vary the soft knob between about 30 and 127 instead of the full range 0 to 127. I was easily able to spot the fault with this visual check. Note that moving the pedal will not change the value shown for the soft knob in the Virus hardware's display.

Simon

Here is a long-needed update on this How To!

1. The process can be greatly simplified if you use the Virus plugin on a computer and assign your pedals to control the soft knobs on that. The computer just becomes yet another box you have to lug to gigs!
2. I no longer recommend the MIDI Solutions Pedal Controller http://www.midisolutions.com/prodped.htm. This sometimes stops working for no apparent reason. It has let me down at gigs. There is one for each pedal, linked in series. So it means that the connected pedal and any whose pedal controller is connected downstream from the faulting one is out of action till it comes right. (So the emergency fix is to remove the faulting pedal controller from the connected series. The pedals connected to the other two pedals will then work.)
3. Instead, I highly recommend the Audiofront's MIDI Expression range of pedal interfaces https://www.audiofront.net/MIDIExpression.php. These did not exist when I wrote the article. The model I use is the 'MIDI Expression iO', the way to go if you connect direct to the Virus rather than a computer, as it supports three pedals and old-fashioned MIDI cables as well as USB. Its advantages over the MIDI Solutions Pedal Controller are:

• It's reliable. I've had mine a few years. It always works.
• One pedal interface, about the size of the MIDI Solutions box, connects multiple pedals. Much less spaghetti on the floor!
• It supports MIDI over USB as well as MIDI cables. So it can be plugged into a computer without a MIDI to USB adapter. Even if you don't want to control software synths, this makes configuring the pedal interface a bit easier.