BCIS 5130: Foundations of Business Presentation Design

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BCIS 5130 Foundations of Business Presentation
Design

• Introduction to MIDI
• Dr. Dan Peak
• University of North Texas

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What is MIDI?

• Musical Instrument Digital Interface
• Standardized and efficient system of
  communication between musical and control devices
• Covers two main aspects
• Data format standards for messaging
• Hardware standards for connecting MIDI devices

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MIDI Uses

• Substitute for, supplement to, effects used
  instead of orchestral sound
• Save money, digital enhancement, digital
  innovation
• Live performance
• Digital applications for network, web, and other
  distributed environments

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MIDI Pros

• Extremely flexible
• Extremely powerful
• No substantial data bandwidth requirements

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MIDI Cons

• Fidelity depends on the available sound
  synthesizer and system
• Requires MIDI systems knowledge to implement
• Requires formal knowledge of music to create
  complex scores
• Requires knowledge of MIDI tools
• Software and hardware issues

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Standard MIDI Limitations

• In a MIDI file, it is the instructions to play
  the notes that are stored, not the audio itself.
• And I repeat The quality of the reproduction
  depends on the synthesizer and sound system used
  for playback.

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Again, What is MIDI?

• Musical Instrument Digital Interface
• Data format standards for messaging
• Hardware standards for connecting MIDI devices

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Data Format StandardsMIDI Messages

• Generally, in the form of a status byte followed
  by one or more data bytes.
• Not all devices implement all of the specified
  parameters
• for example, cheaper keyboards often dont have
  key pressure sensors, and hence dont send key
  pressure data.
• Common messages include Note On and Note Off.

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Data Format StandardsMIDI Messages
1st Byte ()
2nd Byte
3rd Byte
Message
Note On
1001 CCCC
0NNN NNNN
0VVV VVVV
Note Off
1001 CCCC
0NNN NNNN
0000 0000
() First byte may be omitted in the case of a
rapid succession of Note Off or Note Off messages
1st Byte. Channel Range (0-15)
2nd Byte. Note Number Range (0-127)
3rd Byte. Attack Velocity Range (0-127)
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Hardware StandardsMIDI Device Connection
In
Out
In
Out
MIDI USB Port
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MIDI Messages Only Can Travel in One Direction
Through a Cable
In
Out
One-way communication to destination
Two-way communication with two MIDI cables
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MIDI Separates the Functions of Musical
Instruments

• Traditional musicians view the instrument as
  indistinguishable from the sound it produces.
• MIDI separates the
• Keyboard or other interface (controller),
• Recording device (sequencer),
• Instrument (e.g., electronic sound generator the
  synthesizer),
• Synthetic sound (patch), and
• Analog output (speakers).

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Basic MIDI System
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1. MIDIController

• Generates MIDI data when keys/buttons pressed.
• e.g., Note On, Note Off, Channel Number, Program
  Change, Controllers, System Exclusive

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2. MIDI Sequencers

• Software programs. In a very simplistic view, we
  can define sequencers as electronic tape
  recorders.
• Only, instead of recording the actual sounds,
  they record the MIDI messages that are used to
  generate sound.
• They can record directly from a performance, or
  allow composition by entering the notes manually
  (e.g., Sonar, Finale).

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3. MIDI Instruments

• Hardware or software programs that produce a
  spectrum of MIDI sounds, called Patches
• Recreation or imitation of real instrument sounds
• Creation of new instrument sounds
• Creation of impossible and fantastic sound
  effects

• Stored or programmed in a Synthesizer

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4. MIDISynthesizer

• A special-purpose, sound-generating computer.
• Converts MIDI codes to audio signals
• Generates imitation instrumental sounds, directed
  by
• Channel voice messages
• Patches

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Timbre and Patches

• Timbre (pronounced tam-bur)
• Sometimes loosely referred to as a sound or an
  instrument
• Multitimbral
• Capacity of a sound-generating device to render
  more than one timbre at the same time
• Patch (sound)
• A particular timbre generated by a synthesizer
• Piano, violin, electric guitar, drums, choir, etc.

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Patches are Specific Sounds
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Other MIDI Terminology

• MIDI Channel
• Basic system has 16 instrument channels (but
  only one physical channel )
• MIDI port
• Physical input or output on MIDI compatible
  equipment (Unidirectional)

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Location of Ports and Synths

• PC External MIDI IN, MIDI OUT
• For connection to external devices e.g. keyboard
• Microsoft GS Wavetable synth
• Software synth high latency (delay), fairly
  good quality sounds
• FM Synth
• Hardware synth low latency, rather limited
  sounds

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Traditional Music Notation Audio Coding

• Audio coding has actually been around for
  hundreds of years.
• Traditionally, composers record their music by
  writing out the notes in a standard music
  notation.

Beethoven Moonlight Sonata (1815) traditional
notation of audio coding
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Piano Rolls

• A paper roll encoded with punched holes for
  musical notes, duration, loudness
• Player piano mechanically senses the encoded
  holes in the piano roll and depresses the piano
  keys with the appropriate speed and force,
  flinging the hammers onto the piano strings
• Similar encoding concept to 18th Century textile
  loom weave cards, 20th Century computer cards,
  punched paper tape

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Mechanical Player Piano and Piano Rolls
Notes and Durations
www.pianomuseum.com
Pedal and Expression
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Piano Roll General MIDI

• A piano roll can be digitally encoded by
  recording the time when each note begins and
  ends, and other characteristics.

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MIDI PianoRoll View (Multiple Track)
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MIDI Events
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Sonar MIDI Event List
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MIDI Score view
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MIDI Files

• .MID or .MIDI files contain music program
  instructions.
• Basic encoding
• MIDI events / messages (e.g. Note-On, Note-Off)
• The time delay between each event
• Special encoding
• Up to 16 different instruments played at once
• Parameters specifying key velocity, volume,
  special devices, modulation, etc.

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Media Sound Types

• MIDI (for musical composition, background music)
• Digital Audio / Waveform (for voice or
  authentic recordings)
• Storage size waveform bitmap graphic MIDI
  vector graphic

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MIDI versus Digital Audio
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General MIDI versus Extended MIDI

• General MIDI is a computer program with
  limited-quality patches or sounds (128 standard
  voices)
• Extended MIDI supports higher quality depending
  on capabilities of the special hardware and
  software including the number of patches,
  channels, voices, and other factors.

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How is MIDI Sound Created?

• There are two main methods used for sound
  synthesis
• Frequency Modulation and
• Wavetable
• Most synthesizers and sound cards use Wavetables
  for sound synthesis

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MIDI Synthesis Comparison
Frequency Modulation Synthesis (creates
artificial sounds)
Wave Table Synthesis (uses samples from real
instruments)
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What is Wavetable Synthesis?

• An efficient technique for the generation of a
  particular waveform
• One cycle of the waveform is stored in a table
  prior to synthesis
• To generate samples during synthesis, table
  lookup is performed for the desired number of
  samples

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SynthesizerWavetable Processing

• A wavetable is a table-encoded store of recorded
  pitches and other sounds from various musical
  instruments or audible phenomena.
• Pre-processing of analog sounds converts them
  into digital data (digital audio conversion).

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Synthesizer Wavetable Processing

• When a fetch is issued by the synthesizer, a
  table lookup is executed to locate the indexed
  digital sound.
• The fetched waveform is used as the wave model by
  the synthesizer.

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Multiple Wavetables Summed for Impact

• Multiple sounds in multiple wavetables can be
  summed and manipulated to vary synthesized sound
  during execution by time, range, and other
  characteristics.
• Adequate representations of instruments can be
  achieved using only a few basis spectra.

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Wavetable with Three Patches
The patches will be summed into a single
waveform
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Sample Standard Voices

• Bagpipe
• Fiddle
• Piccolo
• Sitar

• Bird tweet
• Seashore

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Demonstration of Professional Sound Tools

• Finale
• Sonar (formerly Cakewalk)