Transcript MIDI and YOU

MIDI and YOU
Orchestra in a Box
What is MIDI?
 Musical Instrument Digital Interface
 MIDI is a protocol - a standard by which two
electronic instruments (as well as other things) can
communicate
 MIDI defines both a physical (wires, plugs and
voltages) and a logical (how the information is
organized) component.
 MIDI only contains the instructions necessary to
“reconstruct” a song. (e.g. sheet music for
electronic instruments)
MIDI Specs
 First defined in 1983 - not much has changed
 31.25 kbaud - serial communication
 Allows for 16 separate channels of information on
a single cable (i.e. it can send information for up
to 16 different “instruments” simultaneously)
 Any parameter can have up to 128 different values
Common MIDI terminology
 A MIDI Controller: generates MIDI messages to
trigger other devices
 A Sound module has a number of pre-recorded
instrument sounds (called patches) stored in its
memory.
 MIDI messages trigger MIDI events – i.e. tell the
sound module which note to play
 A MIDI Sequencer stores MIDI messages and
events in the order in which they happen. These
messages can then be played back – a sequencer is
a multi-track recorder for MIDI instruments.
 DAW – Digital Audio Workstation – a program
that allows you to sequence MIDI and record
audio on your computer
Anatomy of a MIDI message
 There are different types of messages that can do
different things
 MIDI channel voice messages contain the channel
number the message is intended for (1 thru 16), a
command (e.g. note on), and velocity information
(how hard a key is played).
 A typical command is a text message that basically
contains note-number, note-velocity, and note-on
messages - THAT’S ALL!
ex: <channel 1><note 64><velocity 85><note on>
Benefits of MIDI
 File sizes are extremely small, so a large amount
of information takes up a very small amount of
space, bandwidth, and processing power
 MIDI is not limited to musical applications
 Flexibility:
 You can use whatever instrument sounds you wish –
you are not limited to the ones you are physically able
to play
 You can change instrument sounds any time you wish.
MIDI does not care what type of instrument is receiving
the message (i.e. what it is triggering).
 You can easily change or edit a performance – timing,
note duration, pitches – everything can be changed
easily
Downsides of MIDI
 It’s not a real instrument
 Patches are not always standard – you might not
have the same sound set as another person
 “only” 128 possible values for any parameter
 for volume and panning, this can be annoying
 MIDI productions can sound “fake” – both in
terms of sound and performance
 Occasionally “buggy”
 Slow, old, and limited for some things
General MIDI
 General MIDI was an attempt to standardize MIDI
instruments so that it would be easier to use for
long distance collaborations, computer music, and
web-based applications.
 General MIDI devices have specific instruments
assigned to specific numbers so that a device or
computer playing back a MIDI file will use the
proper instrumentation.
 Channel 10 is reserved for drums
 Not all MIDI devices are meant to be General
MIDI compatible
A little music theory…
Pitch
 Pitch is the “perceived fundamental frequency of a
sound” – the “high-ness” or “low-ness” in tone
(not volume) of a given note.
 There are 7 primary pitches which are given letter
names A through G;
 On the 8th pitch, the pattern is repeated, giving us
the octave.
 Western music recognizes 12 distinct pitches per
octave
Octave and note numbers
 MIDI has 128 notes. On a typical Grand Piano
patch, middle C is note 60
 Some programs number the octaves (e.g. -1,
through 9
 The octaves are numbered from lowest to highest,
with C being the start of the octave.
 Each note is named with its letter and octave (e.g.
C4, E4, G4)
 MIDI note numbers are standard; Octave numbers
are NOT
 this can be confusing. (e.g. Middle C could be called
C3 or C4 depending on which program you use, but it
is still MIDI note 60)
Rhythm & Tempo
 Time is divided in bars or measures
 Each bar is defined as having a specific number of
beats
 Each beat is defined as the length of a specific
note (e.g. quarter-note or eighth note)
 This is called meter or time signature; most pop
songs are in 4-quarter (4/4) time
 Tempo = how fast the beats are going
 The same song can be played at different “speeds”
Quantizing
 MIDI uses a “grid” that is defined by note values
 Ie. A quarter-note grid or eighth-note grid
 Notes can be “snapped to the grid” to correct
irregularities (i.e. sloppy mistakes) in the rhythm
 This is known as “Quantizing” or “Quantization”
 If done “incorrectly,” quantization can sound
robotic
Working with MIDI in the box
MIDI Signal Chain
 MIDI flows in one direction
 MIDI devices have three ports: IN, OUT, and
THRU –
 MIDI OUT sends MIDI messages that a device
generates,
 MIDI IN receives the MIDI messages,
 MIDI THRU simply copies any messages that appear at
the MIDI IN port and passes them down the chain.
 Up to three MIDI devices can be “daisy-chained”
without any noticeable latency in the chain
 YOU STILL NEED TO WORRY ABOUT
AUDIO SIGNAL FLOW! MIDI does NOT carry
audio signals
Types of tracks
You need two things when working with MIDI in
a computer:
 You must be able to hear the device. An Aux
Input track might be necessary;
 You must be able to record and playback MIDI
messages. A MIDI Track might be necessary;
 Most programs combine these two tracks into one
for use with virtual instruments. Pro Tools has an
Instrument Track for this purpose.
Virtual Instruments
aka: software synthesizers or “soft synths”
 Virtual - “existing…in effect though not in actual fact” Webster’s II New Riverside Dictionary
 A virtual instrument exists as a plug-in in a DAW
 Plug-in: “A computer program…that interacts with another
[program] to add a specific function…” - en.wiktionary.org/wiki/plug-in
 A virtual instrument is basically a MIDI instrument that
exists in software instead of the real world
 It needs all the same things that an external MIDI
instrument (such as a sound module) would need (except
cables).
Things to consider
 Use a click track or metronome from the very start
 Set your tempo and meter correctly
 Use quantization (judiciously) before you overdub
new instruments
 You can easily change your tempo any time you
wish later on, but something that is not in time
will not work at ANY tempo
THESE THINGS WILL SAVE YOU TIME AND
FRUSTRATION LATER
MUY IMPORTANTE
 MIDI does not generate or transmit any sound or
audio signal whatsoever
 You cannot hear MIDI
 MIDI is only a protocol - a language which
computers and electronic instruments use to
communicate. Humans cannot hear MIDI.
 You can only hear the result of a properly routed
MIDI message, provided it is sent to a device
capable of making sound
 MIDI is NOT digital audio in any way, shape, or
form