Volta is a virtual instrument plug-in that allows users to play and automate modular synthesizers - or any hardware equipped with control voltage (CV) inputs - from their favorite host audio workstation software.

The first product of its kind, Volta receives conventional virtual instrument input such as MIDI notes, MIDI controller data or even high-resolution audio track ramp automation and then responds by outputting a corresponding control voltage signal, which the host software then routes to the outputs of any DC-coupled audio interface connected to the computer. The resulting DC voltage can then drive a standard CV input, such as those found on classic modular synthesizers, modern analog mono synths and even popular effects processors such as Moogerfoogers.

"If you have CV-controlled analog gear that you've been dying to incorporate into your computer-based studio, it's time plug it in and let it rip because now you can use it with same level of convenience and control as a virtual instrument," said Jim Cooper, Director of Marketing at MOTU. "Volta represents a major breakthrough in operating CV gear from Digital Performer, Logic, Live, Reason or any other Audio Unit host software."

MIDI sequencing
Volta allows users to play CV-controlled oscillators with MIDI notes by simply "playing" Volta as they would any other virtual instrument via either MIDI track data or live input from their MIDI controller. Volta converts the MIDI note data to control voltage signals, which then trigger the external hardware. Because host software can pre-buffer MIDI data during playback, the timing between the external hardware audio output and the host software timeline can be sample-accurate (with hosts that support sample-level precision).

Instant tuning and calibration
Analog oscillators are notorious for being difficult to get in tune and keep in tune. In addition, not all oscillators adhere to the tuning standard of 1 volt per octave. But if the oscillator has a CV output, Volta can take care of these issues with one click of its Calibration button. By sending voltages and measuring the pitch response, Volta automatically creates a complete profile that addresses any non-linearities in both the audio interface voltage output and the oscillator. Volta can even tune self-oscillating filters using this closed-loop system. Users can click the calibration button at any time to instantly bring all external gear back in tune.

Virtual instrument operation
As an instrument plug-in, Volta produces mono or stereo audio output to the host software, just like any other virtual instrument plug-in. Volta's output consists of the audio signal returned from the external hardware synth. This means that external hardware, which is already sample-accurate with (and tempo-synced to) the host software timeline, can then be mixed and processed with all of the powerful features of the host software's mixing and effects environment. For example, the host software could be used to arpeggiate the MIDI notes going to Volta (and the external oscillator), and then Volta's resulting audio output could be processed with the host's tempo-synced delay, phaser and reverb effects.

Track freezing
Because Volta operates as a standard virtual instrument plug-in, all external hardware oscillator output playing through Volta can be bounced to disk using the host software's track freezing features. This means you can conveniently "print" external synth audio output at any time for archiving, mastering or future reference.

Complete automation
Volta allows users to automate continuously variable, CV-controlled parameters on their analog hardware (such as filter cutoff frequency, filter resonance or envelope depth) using MIDI CC data (sequenced in a MIDI track or played live from their MIDI controller). If users wish to achieve much higher resolution to avoid possible "zipper noise" and other pitfalls of MIDI resolution, they can instead control Volta using the audio track automation features in their host software. Audio track ramp automation can generate smooth, precise voltage changes at the resolution of digital audio.

In addition to these external automation sources, the Volta plug-in itself provides LFOs, a pattern sequencer, a trigger sequencer and even MIDI beat clocks. These automation sources can be freely applied to any Volta CV outputs, and they can of course be synced to the host tempo and timeline.

A simple user interface
The Volta plug-in window displays 24 sockets at the top of the window that represent audio outputs on the audio interface(s). Control sources (MIDI notes, MIDI CCs, ramp automation, LFOs, etc.) are displayed as icons across the bottom of the window. Users then drag any desired control source icon onto any output socket they wish to control with it. Users can access settings for each control source simply by clicking it.

Each instance of Volta supports up to 24 output slots, and users can invoke as many instances of Volta as their hardware allows. For example, a MOTU PCI-424 system with four 24io interfaces provides 96 channels of output.

Summary of advantages
Volta now makes it easy to use CV-controlled analog gear in today's computer-based studio.

Volta provides:

• Familiar virtual instrument operation: Volta operates within the host software as a standard Audio Unit (AU) plug-in.
• Total recall: All Volta-controlled parameters are saved with the host session.
• Automated tuning and pitch calibration: Volta tunes and calibrates the pitch of external hardware oscillators at any time with the click of a button.
• Sample-accurate precision: The timing between the external hardware and the host timeline can be sample-accurate (with a supporting host).
• Tempo sync: All parameters such as LFOs, etc. can be tempo-synced to the host software.
• Track freezing: Through Volta, external hardware oscillator output can be captured as digital audio using the host software's standard track freezing features.
• MIDI CC control and automation: Play or sequence MIDI CC data to control your external hardware.
• Very high resolution automation: Use host ramp automation for smooth changes without "zipper noise".
• Built-in control sources: The Volta plug-in itself provides tempo-synced LFOs, pattern sequencers, trigger sequencers and even MIDI clock as control sources.