An Introduction To MIDI And Its Use In Electronic

Dance Music

1

Technology can be considered one of mankind’s greatest assets, but ever so often a

user overlooks the intricacies that allows for ease of use. One such intricacy is MIDI,

which has aided many musicians in composing electronic music. Where a traditional

composer needs to have an intimate knowledge of music theory, MIDI has allowed a

musician with a basic understanding to be able to compose music. MIDI’s simplicity

has allowed for a new form of music composition to blossom where a person with

limited resources can produce music in their own ‘Home Studio’.

“Musical Instrument Digital Interface (MIDI) is a digital communications language and

compatible specification that allows multiple hardware and software electronic

instruments, performance controllers, computers, and other related devices to

communicate with each other over a connected network.” (Huber, 2007, p1)

MIDI transmissions or files do not contain any audio or sounds, but instead contain a

data stream, or ‘MIDI message’, which is traditionally used to manipulate parameters

in an external or internal sound module. A sound module, or sound generator, has

the capabilities to create an analog or digital signal, or sound, which can be

manipulated via an external MIDI controller, resulting in audial changes such as a

pitch change of a sound, the amplitude of a sound or how long a sound plays for.

The result from the sound module is an analog or digital signal which can then be

amplified through a speaker system for the sound to be heard by the user (Fig. 1).

Figure 1. MIDI Data And Audio Signal

2

A MIDI message is made up of 8-bit bytes. A bit is a Binary unit, being either 0 or 1.

There are 8 bits in a byte and half of a byte, or 4 bits, is called a "nibble" or “nybble”

(Fig. 2).

Figure 2. Bit And 8-Bit Byte

A MIDI message usually consists of 3 bytes, the first being the Status, or header,

byte, followed by the Data byte(s). The very first bit of each 8-bit byte is called the

Most Significant Bit (MSB) and it determines whether a MIDI message is a Status

byte or a Data byte, which is 1 or 0 respectively (Fig. 3). The Status byte, or Most

Significant Byte (MSB), indicates which “function is to be performed by a device or

program”; and the Data byte, or Least Significant Byte (LSB), which follows after

Status byte, is to “associate a value to the event that’s given by the accompanying

status byte”. (Huber, 2007, p16)

Figure 3. A MIDI Message

As there are 7 bits, there are a total of 128 value variations possible when counting

in Binary code, which is calculated as 27. Although the number of variations of 7 bits

3

is 128, computers and MIDI ‘recognise’ this maximum number as 127 as they start

counting from 0 (Fig. 4).

Figure 4. Status And Data Byte Binary Counting

The 3 bits in the Most Significant Nibble Status byte, after the header bit, are called

Channel Voice Messages and consists of Note-Off, Note-On, Aftertouch, Continuous

Controller, Patch Change, Channel Pressure, Pitch Bend Change or System

command bytes (Fig. 5). (Stanford University, 2012)

Figure 5. MIDI Channel Voices

4

No.1 to 7 of Channel Voice Messages in (Fig. 5) is “used to transmit real-time

performance data throughout a connected MIDI system. They’re generated

whenever a MIDI instrument’s controller is played, selected, or varied by the

performer. Examples of such control changes could be the playing of a keyboard,

pressing of program selection buttons, or movement of modulation or pitch wheels.”

(Huber, 2007, p22)

The nibble that is after the 3-bit Channel Voice Messages is allocated for the MIDI

Channel number, which is often written as “Ch##” where “##” is the MIDI Channel

number. As there are 4 bits allocated to the MIDI Channel number, there are 16

variations possible, calculated as 24. (Fig. 6)

Figure 6. MIDI Channel Numbers

The MIDI Channel numbers give the user more flexibility in where a MIDI message is

sent to. A musician can connect multiple sound modules to one MIDI controller; and

by changing the MIDI Channel number in a MIDI message, they can direct the MIDI

transmission to the device of choice which would be using the same channel

number.

5

Note-On and Note-Off messages (Fig. 7), Channel Voices 1 and 0, which contain the

MIDI channel number in the status byte, have two data-bytes that contain the values

for the MIDI Pitch Number and Velocity respectively, with the velocity being how fast

a key is pressed for Note-On and how fast a key is released for Note-Off. While this

is usually for playing a musically related note, it can also be used for triggering

events in a DAW (Digital Audio Workstation), in which it functions like a binary

switch, the Note-On Message, in binary terms, being 1 or ‘On’ and Note-Off being 0

or ‘Off’.

Figure 7. Note-On / Note-Off Voice Message

Aftertouch comes in two different forms; one which contains two Data bytes, the

Polyphony Key Pressure Voice message, and the one with one data byte, the

Channel Pressure Voice message. When a key has been depressed, there can be

further parametric changes, which can be done via exerting further fluctuating

pressure onto the depressed keys. Polyphonic Key Pressure allows each individual

key to have its own Aftertouch value, whereas Channel Pressure will only have a

“single, overall pressure, regardless of the number of keys that are being played at

6

one time” (Huber, 2007, p25). Aftertouch is often assigned to audial effects that

feature a Low-Frequency Oscillator, such as tremolo or vibrato.

Patch Change messages are to change the sound, or patches, generated from the

instrument. Patch Change messages only contain 1 Data byte which enables a user

to select from 128 patches if the instrument has that many. While the message

seems uncomplex, it is very useful to a user as it allows them to switch patches while

in a performance, which could be automated so the sounds switch automatically.

The Pitch Bend Change message adjusts the pitch of the sound used by use of a

Pitch Bend Wheel. As Huber (2007) said, “… the ear can be extremely sensitive to

changes in pitch”. Because of this, the Pitch Bend Change message uses two data

bytes for one parameter (Fig. 8), resulting in a range of 16,384 steps, however since

Pitch Bend Change also allows for the pitch to descend, this range is more

realistically -8192 values downwards and +8192 values upwards, with 0 being the

unaltered pitch and the centre position of the control (Huber, 2007, p29).

Figure 8. Pitch Bend Range And Two Data Bytes

System messages do not contain MIDI Channels in the Status byte as they are sent

to all channels, or all devices in the network. System messages are split into two

7

categories, System-Common and System Real-Time messages. With the exception

of System-Exclusive messages, they do not contain data associated with the

performance of an instrument, such as playing the keys on a MIDI keyboard, but are

more suited for the global operation of a setup, such as setting the song position

(Song Position Pointer Messages), syncing the clock timing between devices (Timing

Clock Messages) and resetting instruments to their initial power-up settings (System

Reset Messages). (Huber, 2007, p43 – p44)

Control Change (CC), or Continuous Controller, messages are associated with real-

time performance parameters, such as the panning of a sound (CC10), modulation

(CC1) and the Channel Volume (CC7). It uses a Controller ID in the Status byte to

associate which parameter to change.

The Modulation Wheel, or Mod Wheel, is CC1 and when applied, it introduces a

vibrato effect by use of a Low Frequency Oscillator; the intensity of the effect being

stronger the more the control is applied.

Damper Pedal (CC64), Portamento (CC65), Sustenuto (CC66), Soft Pedal (CC67),

Legato Footswitch (CC68) and Hold 2 (CC69) are Switch Controllers, being either

‘On’ or ‘Off’. Usually any Data byte value below 64 will turn the effect off whereas

any value above 64 will turn the effect on. The Damper Pedal will sustain the Note-

On command while the pedal is activated; only transmitting a Note-Off command

once the pedal is released. Sustenuto works like the Damper Pedal, except “… it will

only sustain notes that are currently being played” (Huber, 2007, p37).

All Notes Off (CC123) will send a Note-Off message to all 128 notes on all channels

as a ‘panic’ system in case the system didn’t receive a Note-Off message when it

was supposed to.

8

Omni Mode, CC124 for ‘Off' and CC125 for ‘On’, transmits all data to all MIDI

channels when ‘On’, whereas the ‘Off’ setting will only transmit the data to one

channel.

There are a wide number of control devices available which one could make use of

to record a performance into MIDI data.

As stated by the MMA (MIDI Manufacturers Association, 2012b), “MIDI was primarily

designed for ‘keyboard players’…”. However, there is a wide range of MIDI

controllers available, from basic input systems to some that are more suited for niche

markets. Performance controllers are electronic instruments which can be played

real-time or used to record a performance into MIDI messages.

MIDI Drum Pads controllers, such as the Akai Professional MPC-500 (Fig 9.a), and

MIDI-enabled Electronic Drum Kits, such as the Roland TD-11K (Fig 9.b), are

controllers that are more suited to drumming, or percussive, techniques of playing.

These controllers generally consist of multiple ‘pads’, a flat surface area which

contain sensors to detect impact force, and are physically hit with to generate MIDI

data. The impact generates a MIDI Note-On channel message, the MIDI Note Pitch

being the sound that should be triggered, and the velocity, determined by the

pressure of the impact being higher the harder the pad is struck, which can be

assigned to any parameters that the sound source contains but is generally set to

intensity or amplitude of the playing sound.

The Electronic Drum-kits available are the same size of a real drum-kit and have a

distinct advantage over an acoustic drum set. As sound is generated through the

sound module which the MIDI drum kit is connected to, the artist has the ability to

change the sounds triggered by the pads to whatever their sound source allows,

9

whereas a musician playing on an acoustic drum kit is bound by the current setup at

the time of performance.

Figure 9. MIDI Drum Controllers

“Wind instruments have a number of performance techniques that do not have a

keyboard equivalent – like pitch-pending, changing the timbre or producing

harmonics, all by using extra breath pressure and lip techniques” (Russ, 2007).

‘Wind MIDI Controllers’, otherwise known as a ‘wind synthesizer’ or ‘Electronic Wind

Instrument’, such as the Yamaha WX5, are played like a woodwind instrument.

The unique aspect of this instrument is the ‘breath sensor’ and Breath message

(CC2); the musician blows into the mouthpiece of the instrument and a pressure

sensor inside the instrument measures the force of the musicians breath which is

converted into the corresponding MIDI data. The Breath message is commonly used

to affect the amplitude of the sound, however some devices such as the Akai EWI

4000s utilise MIDI 2.0 which combine the messages of Breath (CC2), Volume (CC7),

Expression (CC11), Aftertouch (Channel Voice message 6) and Velocity (2nd Data

byte of Note-On, Channel Voice Message 2). There is also a lip sensor which will

commonly affect the pitch of the sound, Channel Voice message 7. (Batzdorf, 2006)

10

Figure 10. MIDI ‘Wind Synths’

There are also MIDI controllers suited more for life performance and the operation of

playback events associated with sequencing. ‘Live Performance Controllers’, such

as Novation Launchpad, have buttons which send MIDI data to play sounds or

looped audio files within a DAW project. In the case of the Novation Launchpad, the

‘loops’ or sounds within the DAW are triggered via MIDI Note-on and MIDI Note-off

messages. (Novation, 2012)

Logic Pro, a DAW; an Apple iMac; a FireWire audio interface, the Focusrite Saffire

PRO 40; and a performance controller with slider controls, the Roland PCR-500, was

used to modify and manipulate MIDI data to compose a song. (Fig. 11)

Figure 11. PCR-500 Used In Logic Pro

“I happen to think that computers are the most important thing to happen to

musicians since the invention of cat-gut...” – Dr Robert Arthur “Bob” Moog (1990)

The Environment, in Logic Pro, was utilised to manipulate real-time MIDI data. The

result from the MIDI routing in the Environment was that a single Note-On Channel

11

Voice message would produce a musical triad, as well as replicate these 3 MIDI

Channel Voice messages an octave above and an octave below.

To achieve this, the musical note in the first Data byte of the Note-On message

would be routed into a device called the Chord Memoriser, which allows one to

substitute the Note-On MIDI Pitch Number with a different Pitch Number or have

selected Pitch Numbers added to the performance of the initial musical note played.

The respective musical 3rd and 5th were added to each key, resulting in each single

Note-On Channel Voice message playing a 1,3,5 triad.

This triad, being sent as a 3 separate Note-On messages, in Logic Pro, was then

duplicated and sent into a MIDI data manipulator in Logic Pro, known as the

“Transformer”. The MIDI Pitch Number in the Note-On message was raised or

lowered 12 semitones, being an octave. When a performer is to push a single note

on a keyboard controller 9 MIDI Note-On messages are generated.

Figure 12 . Environment ‘Patch’

For two of the software synthesizers, an “Arpeggiator” was added to the above

manipulation process. An Arpeggiator repeats a note, or sequence of notes. When

only using one note, the Arpeggiator will only repeat that note. When playing more

than one note, the Arpeggiator will play a sequence consisting of the notes in the

chord played. The order of the pattern, the length of the notes and speed at which

12

the arpeggio plays is defined via parameters within the Arpeggiator object in Logic

Pro.

In one of the sounds, this was utilised with the above Environment ‘patch’ to create a

‘chip-tune’, made infamous by 8-bit TV games, by having an incredibly fast

resolution, being note divisions every 1/128th , and short note length, 1/256th notes.

(Fig. 13)

Figure 13. Arpeggio

The hi-hat cymbals in the drum track initially had fixed velocity values throughout its

pattern in the sequencer. The velocity values of the MIDI notes in the sequencer

were altered as to create a groove, similar to the performance of a real drummer in

which every drum hit doesn’t sound exactly the same. (Fig. 14)

Figure 14. No Corrective Manipulation And Corrective Manipulation

13

The performance MIDI controller was configured so that chosen controls on the

instrument, the sliders, would send the correct MIDI message to modify a parameter

in the DAW. One slider was assigned to the CC16, which is a General Purpose CC

message, and through the use of MIDI Learn within Logic Pro, was set to the ‘Filter

Blend’ within the chosen ES2 instrument, ‘Lead – Rhythmic’. The slider was adjusted

from its top position, being 127 in the message’s Data byte, to the lowest position,

being 0. The choice of using the slider was so there was less of a linear feel to the

diminution of the parameter.

The resulting effect on the sound was that there was a shift between 2 filters, going

from a low-pass filter (Filter 2) to a high-pass filter (Filter 1), resulting in the software

synthesizer producing higher harmonics. The MIDI controller was then used to

record automation data, CC16 affecting Filter Blend, into the sequencer of the DAW,

allowing for finer adjustments when compared to using a standard computer

peripheral such as a computer mouse. (Fig. 15)

Figure 15. Automation Via MIDI Controller

MIDI has proven to be a strong standardisation protocol, being 29 years old in 2012,

and in most cases, MIDI version 1.0 is still being utilised. It has remarkably changed

the way musicians compose their music, being a key player in the birth of many new

genres of music.

14

MIDI has allowed for the layperson with simple music knowledge to be able to freely

express their creative side and compose music, where this may not have been

possible without the invention of MIDI. As more and more devices are released with

MIDI compatibility, it becomes a more and more useful tool to learn and understand.

15

Bibliography

AKAI (2012a) Akai MPC1000 [Online image]. Available from: http://www.akaipro.com/stuff/contentmgr/files/0/0717ce0054b74108faef329855c5a0bf/medium/mpc1000_top_med.png [Accessed 30th November 2012]

AKAI (2012b) Akai EWI 4000s [Online image]. Available from: http://www.akaipro.com/stuff/contentmgr/files/22/752b524af67019860ede24adc7e19825/medium/ewi_front_md.png [Accessed 30th November 2012]

BARNES, D. (1997) More about MIDI. [Online] Available from: http://mmlweb.rutgers.edu/music127/midi/more_midi.htm [Accessed: 30th November 2012].

BATZDORF, N. (2006), Akai EWI 4000s Electronic Wind Instrument. [Online] Virtual Instruments Magazine. Available from: http://www.virtualinstrumentsmag.com/VI_Dec06.pdf [Accessed: 30th November 2012]

DC Cemetery (2012) DC Cemetery. [Online] Available from: http://www.dccemetery.net/welcome.htm [Accessed: 25th November 2012].

HUBER, D. M. (2007) The MIDI Manual. 3rd Edition. Burlington: Focal Press.

MIDI Manufacturers Association (2012a) MIDI Glossary. [Online] Available from: http://www.midi.org/aboutmidi/glossary.php [Accessed: 29th November 2012].

MIDI Manufacturers Association (2012b) MIDI Products. [Online] Available from: http://www.midi.org/aboutmidi/products.php [Accessed: 29th November 2012].

MIDI Manufacturers Association (2012c) MIDI Messages. [Online] Available from: http://www.midi.org/techspecs/midimessages.php [Accessed: 29th November 2012].

NOVATION (2012) Novation Troubleshooting Guide .: Novation Answer Base. [Online] Available from: http://www.novationmusic.com/answerbase/en/article.php?id=658 [Accessed: 3rd December 2012]

PATCHMAN (2012) Patchman Music Yamaha Store [Online image]. Available from: http://www.patchmanmusic.com/YamahaWX5medium.jpg [Accessed 30th November 2012]

POINT BLANK ONLINE (2012) Point Blank Online School. [Online] Available from: www.pointblankonline.net [Accessed: 29th November 2012].

16

REEDER, J. D. (2000) Tutorial - Data lines, bits, nibbles, bytes, words, binary and HEX Available from: http://www.learn-c.com/data_lines.htm [Accessed: 30th November 2012]

ROLAND (2012a) TD-11K [Online image]. Available from: http://www.roland.com/products/en/TD-11K/images/top_M.jpg [Accessed 30th November 2012]

ROLAND (2012b) PCR-500: USB MIDI Keyboard Controller [Online image]. Available from: http://cms.rolandus.com/assets/images/products/gallery/pcr_500_top_gal.jpg [Accessed 30th November 2012]

RUSS, M. (2008) Sound Synthesis and Sampling. 3rd Edition. Burlington: Focal Press.

STANFORD UNIVERSITY (2012) MIDI Roadmap of the Byte. [Online] Available from: http://253.ccarh.org/handout/bytetable/bytelist.pdf [Accessed: 29th November 2012].

SYMBIOSIS MUSIC (2005) INTERVIEW WITH BOB MOOG. [Online audio] Available from: http://www.symbiosis-music.com/sounds/Bob_Moog_2_(c)_Symbiosis.mp3 [Accessed: 30th November 2012]