A Guide To USB Controllers, MIDI And Audio In Music Recording

Audio Interface Basics

The are numerous Control Surfaces (knobs, buttons and screens to you and me) and USB Controller Keyboards currently on the market, offering users a huge variety of products to hook up to their PC or MAC based recording platform. Many of these interfaces now offer tight integration with the big name audio/Midi sequencing and computer music packages, like Cubase, Ableton, Propellerhead Reason and Avid Pro Tools.

This is useful when you understand how to use them, but it may present barriers for potential users who are trying to select the best option for their particular needs. For example, someone looking to work predominantly with loops and samples may opt for Ableton, whilst a songwriting guitarist might opt for Presonus Studio. In this article, we're looking to shed some light on these products and hopefully take some of the undoubted mysticism that can surround computer recording. Essentially, we want to help users to better assess what products they need for the results they are striving to achieve.

USB MIDI Interfaces

There are currently more USB interfaces and products within the music industry than you can shake a stick at, with more being released on what feels like a daily basis. To me, it makes perfect sense to cover what constitutes a USB interface before we go any further, as moving forward without understanding this fundamental concept is akin to walking into a minefield.

In short, a USB interface can be classified as basically any device that plugs into a PC or Mac via USB, however some USB devices offer only MIDI support whereas others support both audio and MIDI interfacing (see this SoundonSound article for an interesting commentary on MIDI over USB speeds). This point is of fundamental importance as, if you buy a USB MIDI controller keyboard to run soft synthesizers on your computer, you are not going to hear anything unless you also have an audio interface, a pretty important point to note! So what is MIDI, how does it vary from audio and what products tend to only feature USB MIDI interfacing without support for any audio?

Midi is simply control information generated by Midi compatible products, for example a USB controller keyboard. Note that when a note on such a product is pressed, the keyboard generates a Midi note on message (for example which note has been pressed, related velocity information, i.e. how hard the key was struck) and then a midi note off message when released. There is no tonal or audible content to these signals they are just messages.

Connecting your Kit

An appropriate analogy to consider at this point is a stand alone hardware synthesizer. Any hardware synth can be broken down into three main component parts: a MIDI trigger keyboard, a Sound Module and its audio output stage. When you play a note on the keyboard, it sends MIDI information to the inbuilt sound module, which in turn generates/synthesises appropriate pitch and sound information that is then passed to the digital to analogue converts at its output stage. Users can hear what they play by simply connecting speakers or headphones.

Considering a computer based recording setup, a USB MIDI Controller keyboard is in essence just a MIDI trigger keyboard bundled with a USB MIDI interface. The connected computer will record this information and pass it to either an external sound module or an internal soft synth/sampler package. However, if using an internal soft synth or sampling package it is a requirement of the PC or Mac to use an ASIO compliant sound card, or audio interface. By connecting either headphones or monitor speakers to the USB audio interface will be able to hear the audio played back.

Therefore, a USB MIDI controller keyboard simply generates MIDI note information along with related parameters, which are fed to a PC/Mac setup via its inbuilt USB MIDI interface. A computer music recording package, e.g. Cubase, can record this information and display it for easy editing, etc. However, to generate sound from the USB MIDI keyboard you will need either an external sound module hooked up to the system or to be running a software synthesizer. USB audio interfaces generally feature microphone and instrument inputs, which also allow users to record actual audio tracks with an appropriate software package along side MIDI tracks and build complex songs.

In the old days, those clever enough and with serious time on their hands were able to benefit from the numerous advantages that the MIDI protocol offered by creating MIDI maps. This technique used continuous controller change messages (CC) in addition to MIDI Machine Control (MMC) to yield easy (once programming was out of the way!) hands on control over various parameters. A technical explanation of MMC is available at http://home.roadrunner.com/~jgglatt/tech/mmc.htm.

MIDI Machine Control

MMC offers standardised functions in MIDI for stop, play, record, etc. offering remote control of sequencers and digital audio workstations (DAWs). However, much greater functionality could be achieved by taking advantage of continuous controllers. There are 128 Continuous Controllers available within the MIDI protocol, ranging from 00 to 127, some are to control volume (e.g. CC 7), or modulation (CC 1), but numerous are unassigned.

This enables users to link up functions, e.g. a MIDI slider/controller to control say volume of a specific channel on a software mixer by making the correct assignment. This can be a laborious task, however recent developments by numerous manufacturers (e.g. Novation with Automap technology) have allowed their products to analyse any given MIDI setup and automatically map the correct assignments giving instant hands on remote control over various parameters.

Those new to computer music simply have no idea how complicated and mind blowing this whole area was in the early days – we’re talking science degrees just to link a few boxes together! So, no matter how hard it appears to be, just apply a bit of logic as it's essentially plug-and-play these days.

By Andy Atkins

Andy Atkins is, maybe surprisingly, a non-tech writer on music gear and musicians, who definitely prefers picking-up a guitar to picking-up an audio interface. He's written for some of the biggest brands in the music equipment industry over the years and can, very occasionally, be seen as a guitarist/soundman in an ageing band.