Audio and MIDI
As you probably already know, when working with music, two main types of sound representation are used – these are Audio and MIDI.
Audio (lat. Audio “hear”) is a general term related to sound technology. Often, the term audio refers to sound recorded on sound media; less commonly, audio means recording and reproduction of sound, sound recording and reproducing equipment.
Audio and MIDI (Audio vs MIDI)
Audio equipment works with signals including frequencies up to 20 kHz, since higher frequency sound is not perceived by hearing.
MIDI (English Musical Instrument Digital Interface – a digital interface for musical instruments) is a standard for hardware and software that allows you to play (and record) music by executing / recording special commands, as well as the file format containing such commands. The playback device or program is called a MIDI synthesizer (sequencer) and is actually an automatic musical instrument.
Audio – this is what was previously recorded on tape recorders, vinyl discs, that is, audio was originally analog in nature. With the introduction of the computer in working with sound, the audio has become digital and the sound cards of the computer work only with digital sound. The stream of numbers began to determine many parameters of sound reproduction. The advantages and disadvantages of digital sound can be argued hoarsely, but the fact remains that digital recording and playback are used everywhere today, like digital photo and video. All CDs and DVDs that you listen / watch are digitally recorded.
I will not talk about multichannel and three-dimensional sound here – this is a separate topic. And the fact that the sound is mono and stereo, too, I hope, in general terms, everyone has an idea about this. I note that mono is a single-channel sound, and stereo are two independent audio channels.
Sound on a computer can be recorded and reproduced with a given (defined) level of sampling frequency and bit depth.
Sampling frequency (or sampling frequency) – this means how many times sound information is transmitted in one second, that is, the sampling frequency of a continuous signal. For example, the standard frequency for a music CD is 44100 Hertz or 44.1 KHz. This means that when playing a sound, information on a file is transmitted 44100 times to the sound card in one second, 44100 times.
Bit depth of sound – this means how many bits of information about the sound are transmitted each time, with each transmission. 16 Bit is a CD standard. And if you see the image of the parameters in this form – 16/44, then this is a display of the bit depth of the sound (16 bits) and the sampling frequency (44 KHz, rounded).
And the higher the frequency / sample rate, the better the sound. In recording studios, to get the best quality, they work with high rates – 24, 32 bits and 96 kHz or more. And then, when preparing music for publication on a CD, they translate it into lower indices of the CD standard – 16/44.
There are a lot of audio formats.
The most common are such as:
CDA (Audio CD) is a regular CD with high quality sound.
WAV is a standard Windows file used on a computer.
Lossy compression formats:
MP3 (MPEG-1, Layer3) – providing acceptable sound quality at high compression ratio. The most popular format today. The sound quality of compressed sound depends on the bit rate (data stream size). The lowest acceptable bit rate is 128 kBit per second. Accordingly, the higher the bitrate, the better the sound quality.
WMA (Windows Media Audio) – a format from Microsoft. With smaller file sizes, it is approximately identical to MP3 quality.
OGG Vorbis – this format is superior in quality to MP3 at similar bit rates, but historically, MP3 has conquered the world market earlier.
RealAudio is a format for transferring sound to the Internet. The ultra-low bitrate and, as you know, the appropriate quality, but is very suitable for a slow Internet.
Now about the MIDI interface.
The introduction of digital technology into music has created a fundamentally new sound recording format for MIDI (Musical Instruments Digital Interface), which means the digital interface of musical instruments.
You need to clearly understand that the MIDI format is not a sound recording, as such. Only “orders” to the sampler or synthesizer for performing actions aimed at extracting sounds are reflected in the stream of MIDI commands. And the MIDI protocol does not transmit the sound itself with its vibrations, but only commands to play it.
According to modern computer concepts, there are not so many “orders” in the process of sound extraction and they cover the main sound parameters: instrument timbre, pitch, volume, duration, panorama, frequency modulation and many others.
Almost all modern electronic instruments and sound cards work with the MIDI format. It was created so that the instruments of different companies (synthesizers, samplers) could respond equally well to the same commands.