Audio and Midi
The differences between digital audio and its original sound source are an essential part of understanding how digital music is produced. Midi, (musical instrument digital interface) can alleviate some of the heavy workload that processing audio files can require. Digital audio, midi, music software synthesizers and samplers; can all coordinate to provide a digital audio workstation that caters to your creative preferences. In this section, I will explain key points of audio and midi, including the fundamental differences between audio, audio signals, digital audio, and midi data - as they relate to music production in a home recording studio.
In a digital audio workstation, audio is received in one of the two following forms by an audio device before it can be recorded.
Sound Waves - Are vibrations through the air. (What you hear) The frequency of an audio recording is graphed as a waveform.
Electrical Signals are varying amounts of voltage that carry carrying musical information through the signal path. (I.E. Recording into a microphone converts the audio into an electrical signal, or, an amplifier transmits analog signals.)
Microphone Recording:
1) Acoustic instruments emit sound waves that are recorded into a microphone.
2) Microphones transfer the sounds into electric voltage, which is called the signal.
(The amplitude and frequency are the same as the sound wave being recorded into the microphone.)
Analog signals must be converted into a digital file before it can be recorded onto digital audio tracks, and stored on a digital medium. However the analog signal can be sent to an amplifier and external speakers to be monitored in its current format. Further, it can be sent to an analog recorder (i.e. reel-to-reel) for printing the audio onto cassette tape.
Analog recorders, and multi track tape recorders - have been the standard for audio recording and music production - only up until recent advances in digital audio over the last several years.
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MIDI (Musical Instrument Digital Interface) is a computer-generated data protocol that triggers tones and tells them when to start and stop, how loud to play these tones, (velocity) and other informational commands. It is important to understand that MIDI is not audio, and cannot be processed or edited the same way.
MIDI has been used since it was introduced in 1983. The last couple of decades have made it a standard computer format that is universally compatible. Midi has become very efficient for composing digital music since it uses much less hard-disc space or processing power than audio file formats.
In review, audio is a live sound. Audio is received by a microphone and transmitted as a signal. Audio is the original vibrations made by an acoustic guitar, a vocalist, etc.
It is sent as an electrical signal to any desired destination, such as a recorder, amplifier, etc. Recording the original audio signal using music software - is done by converting the audio signal into a digital audio file. This conversion happens when the signal passes through an analog to digital converter in an audio interface or soundcard. This is a hardware device needed to translate the analog signal into a digital audio recording.
Midi is computer data that is recorded and read back on command by your computer. This information is used to triggers sounds, then together record both elements using an audio and midi sequencer. The song file and all relative audio file components are stored onto hard disk for the convenience of random access editing.
MIDI uses significantly less computer resources for track recording and mixing. It is now a standard music composition tool. Midi has advanced over the last couple decades to now being a revolutionary composition and production tool.
