PA3 Derailer: metal bars and springs colide in physical modelling virtual synth

04 Apr 2018 by Robin Vincent | Approximate reading time: 2 Minutes

Physical Audio PA3 Derailer · Source: Physical Audio

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Derailer builds a physical modelling synthesizer through a combination of metal bars and springs. The metal bars can be struck or bowed and connected to other bars via non-linear springs. As the bars are played the springs cause sympathetic resonance in other connected bars. The result is haunting, expansive and has this sense of danger as the resonance builds towards chaos. I like it!

PA3 Derailer

Derailer uses “finite-difference time-domain numerical modelling”. You have a box of 37 tuned strike bars, 5 resonator bars and up to 81 spring connections to play with. All sorts of variations can be teased out by manipulating the various physical parameters. With the metal bars you have control over mass, stiffness, decay, boundary and output position. The springs offer strength or angular frequency, nonlinearity, connection position and whether they are on or off.

From what is essentially two objects you can build quite a complex modular system of sound generation.

They have a lot to say about MIDI control, urging the use of mod wheels, control sliders and aftertouch in order to take full advantage of the parameters in performance. Their videos tend to feature the ROLI MPE keyboards which are completely ideal.

Getting into the GUI

The user interface is quite interesting. The strike bars are grouped into octaves and below them are the resonator or drone bars. The spring connections between them can be freely moved, changed or deleted. Selecting objects in the central window gives you information and parameters in the side window. One note to make is that the 37 strike bars all share the same attributes, whereas the drone bars can be edited individually.

The struck sound is very reminiscent of a marimba or other tone bar based instrument. Derailer has an inbuilt “multi-strike” arpeggiator which when combined with some mod wheel action produces some amazing rhythmic performances. Bowing is applied to the first drone bar and has up to 3 note polyphony as opposed to unlimited polyphony with striking. Using connections to other drones and nonlinearity you can push it into self-resonance.

All in all Derailer has the ability to fascinate. Generating very pleasing results in unusual ways. And it’s software doing what software does best rather than simply emulating hardware electronics.

PA3 Derailer is available now for £159, it’s MacOS only and there’s a free demo version to try out if you wish.