Diving deeper into the Pro-1
> The Pro-1 has a few more tricks up its sleeve. Oscillator B can be disconnected from the keyboard by a switch on the front panel – this is handy for creating drones or sound effects. Flipping the lo freq switch to on lets the oscillator frequency sweep across a larger range of pitches, from below the audible range to way up into audio rate modulation. This is useful as Osc B can be used as a source in the modulation matrix and taken out of the mixer fully, adding yet another way to modulate something in the Pro-1. While many modern synths boast modulation matrices with far more options, destinations, and variables, the modulation matrix on the Pro-1 is one of its most unique features. Three sources (filter envelope, Osc B, and the LFO) can be routed to five different destinations: both frequency and pulse-width amounts for each oscillator, as well as the filter cutoff. These sources can be sent either ‘directly’, where the depth is controlled by the amount knob, or through the modulation wheel on your MIDI keyboard.
What’s even more useful is the fact that all of the modulation sources are also doubled via the aforementioned patch jacks on the front panel. This means it’s possible to modulate parameters of the Pro-1 either using the modulation matrix or via patching with other Eurorack gear, or both at once! Integrating the Pro-1 into your pre-existing system is as easy as unscrewing four screws and disconnecting the power supply.