USB MIDI Controller Keyboards – Under the Hood
What is MIDI?, Why do I get a delay when playing an
instrument from my keyboard? What are MIDI CC messages?
If you are new to MIDI and computer music all
of this may seem very daunting but do not despair, it’s not as complex as it
may seem. With MIDI as with almost everything else, basic knowledge is enough
to get you going and expertise can evolve while you do what you enjoy the most,
the creation, making and recording of music.
First things first, getting the system up and
A typical computer music setup consists of a PC or
Mac computer, music software (some products are referred to as DAW’s), a USB
controller Keyboard such as Acorn Instruments Masterkey, a sound card and a
- The keyboard is connected via USB to the
- The computer runs the software.
- The keyboard controls the software.
- The software generates digital information
representing the sound.
- The sound card converts the digital sound
information in to analog signals.
- The analog signals activates the speakers and
then generates the sound that you hear.
Getting a system up and running for the first time
therefore involves installing software, updating operating systems and
installing drivers. Thankfully the MIDI controller part of it is typically
easy, particularly if you have bought a USB class compliant device such as the
Acorn Instruments Masterkey. That a device is class compliant means that
it complies with USB standards and therefore uses a generic USB driver
implemented in the operating system. There is therefore no driver to install
and a USB class driver is seen by the operating system when the device is
connected via USB.
A USB class compliant controller keyboard can be
plugged in to any windows computer from Windows XP and up or Mac OSX, without
installing any driver.
Installing music creation software is no different
than installing any other piece of software. Make sure your computer meets the
recommended system requirements and make sure to check the manufacturer’s
website for latest updates. The most common type of software is called a DAW an
abbreviation of Digital Audio Workstation. A typical DAW has the ability to
record and play back multiple tracks of audio or MIDI, run plug-ins to add
audio effects and virtual instruments (also called VI’s) plus provide audio and
MIDI editing facilities. The VI is a software plug-in or standalone software
product which generates the sound triggered by the USB controller keyboard,
when you hit the key. Without a VI the keyboard would not trigger sound in the
computer system so its important to check that your DAW has some instrument
plug-ins as standard. The Presonus Studio One Artist product that’s included
with Acorn Instruments Masterkey series comes with 3 different instruments as
standard. If you are using another DAW, make sure to check that it already has
VI’s included and if not, check which ones are available for it.
DAW’s as well as stand-alone instrument software
work with a USB class compliant device so once you have plugged in your
keyboard, installed the software, you have completed the first part.
The following is a list of some manufacturers of
music creation and standalone instrument software:
Sound cards come in many shapes, sizes and
configurations. In fact, a modern computer will often come with a sound card
build in for the purpose of playing back music or for use with Skype etc. A
build-in sound card can be good enough in the beginning but there are several
reasons why you may want to consider a separate option.
- Build in sound cards can have very high audio
latency. Latency is the time it takes for the audio to travel from the
software, through the operating system and the driver to the sound card
before finally being played through the speakers and reaching your ears.
If you hear sound delayed either when recording through an audio input or
by playing a VI from your USB controller keyboard you are experiencing
- Quality of sound. Because build-in sound cards
are typically designed for communication and not music making, the quality
can be very poor, and is at best, average.
- You may also want more options that the
typical stereo in/stereo out configuration that are typical of build-in
A sound card consist in its most basic form of an
Analog-to-Digital converter (A/D) and a Digital-to-Analog converter (D/A). The
A/D converts an audio signal from the analog domain to digital binary data
which the DAW can work with.
The D/A does the reverse by converting digital
binary data to an analog signal that can be amplified by the speaker system.
In essence, you use the A/D to record sound in to
the computer and the A/D to play back the recorded sound or play back digital
sound created by a VI. Whether you record or play back, its sensible to have as
low a latency as possible (its not possible to eliminate latency entirely, only
keep it below a noticeable level). A good sound card will therefore come with a
custom sound card that optimizes the path from the software to the DA
delivering latency performance below 10ms. When choosing a sound card, you may
also want to consider what kind of input and output configuration you will
need, how many mic pre amps as well as headphone sockets as well as of course
the performance specifications. When installing the driver for your chosen
sound card, always check for the latest version on the company’s website. Often
the drivers supplied with a product are not the latest, due to the lag time
between driver updates and rolling in to production.
Here is a list of some manufacturers who offer
sound cards for computer music products.
With the keyboard connected, software and sound
card installed the last step is to connect a speaker system to the output of
your sound card. With all that done, create an instrument track in your DAW,
make sure a VI is selected, play the keyboard to make sure you are getting a
signal by checking the mixer metering and then turn up the volume of you
speaker system gradually. Your computer music system should now be alive.
Recording with a USB MIDI controller keyboard
With everything up and running, it’s easy to record
your performance in your DAW. Every DAW has transport similar to that of an old
fashioned tape recorder (remember those) so simply press the usually red record
button and start playing. When you stop the recorder, you should see your first
part in the arrangement window. But what you have recorded is not sound. When
you record with a USB controller keyboard such as Acorn Instruments Masterkey
series, you record MIDI data rather than audio.
MIDI is an abbreviation of Musical Instrument
Digital Interface and was conceived in the 1980’s to allow electronic
instruments to talk to each other. You can read more about it on the MIDI
Manufacturers Association’s website http://midi.org.
In its most basic form, MIDI simply sends data of
movement. So when a key is hit on the Masterkey USB controller keyboard,
Masterkey sends information such as which note was played, how long it was
played for and at what velocity level (force). This data is then recorded by
the DAW for further editing. If you open the MIDI edit window in your DAW
following the recording of MIDI data you will see a grid window which is
somewhat similar to how the old self-playing player pianos you see in westerns
work. Paper would move from one roll to another at a steady tempo with cutouts
in the paper telling the mechanics which note to play and for how long. Punch a
few holes in the paper and more notes would play, whether desirable or not.
The MIDI editor works the same way but with the
added convenience of modern software technology. You can move the note both in
terms of time and note value, change its length and change the velocity it was
played with. The flexibility of being able to perform detailed editing on a
note by note basis is what makes MIDI attractive over say just recording the
audio of an instrument to an audio track. You can even delete or insert notes
just like you can add and delete letters in a word processor.
But there is more to MIDI than note events. An
event type called a MIDI Continuous Controller event (or MIDI CC) allows you to
control parameters on the VI. The Acorn Instruments Masterkey USB controller
keyboard series for example has two wheels labeled pitch bend and modulation.
When you move the pitch bend wheel, you will increase or decrease the pitch of
the note. Moving the modulation wheel will add modulation. These are standard
parameters that all instruments respond to and each will be recorded by the DAW.
Typically the editor will have a lane window which shows the curves of your
movement once the data is recorded and you can use a pencil or line tools for
Because of MIDI CC’s its therefore possible to
control parameters in your DAW and not just musical note data. You could for
example control volume in your audio mixer, effects parameters or every single
parameter in a VI for quicker and more tactile editing. On Acorn Instruments
Masterkey series USB controller keyboards we added 4 MIDI CC pots and 1 fader
for this purpose (as well as the pitch bend and modulation wheels). These are
set to the standard MIDI CC values for controlling the following parameters:
Fader 7 Volume
C1 74 Brightness (cut-off)
C2 71 Timbre (Resonance)
C3 73 Attack time
C4 72 Release time
For a complete list of MIDI CC’s, click here http://www.midi.org/techspecs/midi_chart-v2.pdf and
check page 6. The entire pdf document is excellent reading for a more detailed
insight to MIDI messages.
Many DAW’s have the ability for a parameter to
learn a MIDI CC. If yours doesn’t, you may need to consult the software manual
as there may be a software chart that shows which MIDI CC to program to control
a particular parameter. MIDI CC’s allow you to experience software products as
if they were hardware but it also enhances your creative options by enabling
you to edit your controller movements.
If you are new to USB controller keyboards and MIDI, get started by reading our under the hood guide. How it all works is explained in simple terms with links to websites that can help you with more in-depth information.