One of the more popular free devices posted on maxforlive.com in 2013 was Spektro Audio's CV Toolkit, a Max For Live instrument that was designed not to make sound but to generate control voltage signals for modular synthesizers. The device was popular enough that some in the modular community (those that don't use Ableton, mostly) requested a standalone version. Thankfully, Cycling '74 now provides a workflow that (with a bit of effort) allows you to convert Max patches to standalone apps, so the transition was a natural one for the CV Toolkit. During this process Ferre added some new features and a Lemur interface that allowed CV Toolkit to be controlled via iPad. The resulting product was then offered for sale on Spektro Audio's website for $15.
Like pretty much all CV-generating software, CV Toolkit requires a DC-capable audio interface to work its magic. While there are now Eurorack-style interfaces available from manufacturers like Expert Sleepers dedicated to this task, many traditional audio interfaces also work. I tested with a MOTU Traveler without any problems. Once you have your hardware sorted, getting CV Toolkit up and running is as simple as opening the application, selecting your audio interface and turning it on. Using the standalone version of CV Toolkit alongside a DAW gets a bit complicated, though. Since multi-client ASIO is not possible (you might have some success using ASIO4ALL) your best bet is to use two audio interfaces, one for the DAW and one dedicated to CV Toolkit. MIDI Clock synchronization from a DAW is much more straightforward, though, so getting CV Toolkit "in time" with your session is easy.
As I said before, CV Toolkit essentially provides different ways to generate control data for modular gear. This includes three LFOs (two traditional and one dedicated to sample-and-hold), two attack/decay envelopes, one breakpoint envelope, one step sequencer and an advanced generator called a ScanGraph. The latters lets you draw a breakpoint envelope and then scan through it in two ways: manually with a dial or automatically by routing any other signal to it. The result is a constantly sent value based on the location of the envelope currently being scanned.
In addition to the generators, there are a few modules that don't generate signal on their own but process the signal from other modules. The first is the Mix processor, which, as the name suggests, mixes two signals. Then there is the Slew processor, which is used much like the portamento control on a synthesizer to round off the edges of a stepped signal. Finally, the Biased Switcher takes in two signals and periodically chooses one or the other to output. The interval time and the probability of each signal being chosen are the two main controls here.
The signal produced by CV Toolkit's generators can be routed to any of the eight audio interface outputs using the routing matrix, which is an X-Y coordinate matrix just like the one found on the legendary EMS VCS 3 synthesizer (or like the one in the classic Battleship board game). The signal sources are the rows of the matrix, and the possible destinations are the columns. To route a signal to an output you simply click on the correct intersection in the matrix. The processor modules show up as both destinations and sources, so you can for example route the step sequencer output to the Slew, and then the Slew to one of the outputs. Overall the routing matrix works quite well, but the usability suffers a bit towards the bottom rows: since the destination labels are only displayed along the top edge, I found myself having to trace an imaginary line in order to find the right place to make the connection. (The recent 1.1 update adds a feature that provides some visual guidelines.)
Other usability troubles we found in the CV Toolkit include the lack of gain controls on anything other than the LFO modules. The routing matrix has a global trim control, but it would be nice to be able to, for example, restrict the range of the step sequencer or scan graph. Using the trim for this is not ideal, as it will alter other signals like gate as well. Also, activating the tempo synchronization of any of the generators didn't seem to reset the phase—an additional button to reset all controls to match the clock would be useful. The version I tested didn't offer traditional MIDI-to-CV voice control, requiring that you run it alongside something like Silent Way or MOTU Volta; the latest update has added this feature.
When it comes down to it, though, the CV Toolkit turned out to be quite a useful tool, especially with the included Lemur interface. This kind of control at the touch of a finger is an inexpensive way to add the equivalent of hundreds or thousands of dollars worth of modules, bringing new variety to your CV-capable gear. I began to have visions of using it to control MIDI gear as well—maybe in the second version, the routing matrix can include MIDI CC outs. As-is, at $15, CV Toolkit is a must-own for modular users.
Ease of use: 4/5