SIENA COMPUTER CLUB

http://audacity.sourceforge.net/  - Audacity is a free, open source audio recorder/mixer

There are basically two types of sound cards - the FM Synthesizer and the wave

table lookup (samples). In the FM Synthesizer, the chip understands the

characteristics of various sounds, and creates these on the fly, so to speak.

The wave table lookup, on the other hand, actually stores recorded samples of

the sounds in the hard drive or card buffer, and works by assembling these

sounds into the correct arrangements. The wave table lookup types tend to be

pricier than the FM synthesizer, but the sound quality is normally richer and

with deeper harmonics.

There are three major groups of audio file formats:

    * uncompressed formats, such as WAV, AIFF and AU.

    * formats with lossless compression, such as FLAC, Monkey's Audio (filename

extension APE), WavPack, Shorten, TTA, Apple Lossless and lossless Windows Media

Audio (WMA).

    * formats with lossy compression, such as MP3, Ogg Vorbis (filename

extension OGG), lossy Windows Media Audio (WMA) and AAC.

Lossy file formats are based on psychoacoustic models that leave out sounds that

humans cannot or can hardly hear, e.g. a low volume sound after a big volume

sound. MP3 is such an example.

There are many newer audio formats and codecs claiming to achieve improved

compression and quality over MP3. Ogg Vorbis is an unpatented, free codec.

Microsoft has its Windows Media Audio format.

What's the Difference Between Audio File Types?

There are a handful of audio file types you should be familiar with if you are

planning to copy music off the Internet or even copy a CD. If you aren't sure

what file types you are working with, you can distinguish any file type on your

computer by the extension in the file name. The extension is the set of letters

that follows the dot, as is in: seashore.wav.

    * Waveform Audio (.wav)

      Waveform Audio (.wav) is a common file format. Created by Microsoft and

IBM, WAV was one of the first audio file types developed for the PC. WAV files

are defined as lossless, meaning that files are large and complete; nothing has

been lost. Professionally recorded CDs are also a lossless audio source.

      In contrast, the three audio formats listed below are lossy-redundant and

non-auditory data is removed to allow for more compact storage; in essence, some

data has been lost. This process of removing data to shrink the file size is

called compression.

      The three file formats below must begin with a lossless format-such as a

store-bought CD or a computer WAV file-then compress it. Most lossy formats

boast little or no detectable change in sound quality. But because each

compressing format selects the deleteable data differently, converting one

compressed file into another lossy format will sometimes result in lower quality

audio. Again, always start with a CD or WAV file, then compress.

    * MPEG-1 Audio Layer 3 (.mp3)

      MPEG-1 Audio Layer 3 (.mp3) is a common, compressed WAV file. MPEG-1 files

are about one-twelfth the size of WAV files. This is why MP3 players can

accommodate hundreds of songs on a tiny chunk of storage space.

    * Windows Media Audio (.wma)

      Windows Media Audio (.wma) was developed to compete with the MP3 format

for Windows Media Player. Microsoft claims that the WMA files are compressed

three times more than MP3s yet retain their original sound quality.

    * Ogg Vorbis (.ogg)

      Ogg Vorbis (.ogg) is another compressed source code similar to MP3, but

like WMA, more compressed. Ogg Vorbis is also open source (free to all,

unlicensed, no strings attached). While MP3 compresses data at a constant bit

rate, Ogg uses a variable bit rate. To illustrate-if you are copying chunks of

silence into MP3 format, the compression bit rate stays the same as if you were

compressing the sound of an entire orchestra. But if you are copying chunks of

silence into Ogg, your compression rate will drop to nothing. The rate varies

with the need.

Other Audio File Types

    * Musical Instrument Digital Interface (.midi)

      Musical Instrument Digital Interface (.midi) is commonly used for computer

keyboards and other computer-based musical tools. MIDI files contain musical

notes, rhythm notation and other information often needed by a composer.

    * Audio Interchange File (.aif, .aifc or .aiff.)

      Audio Interchange File (.aif, .aifc or .aiff.) was developed for the

Macintosh computer to store audio files.

    * Sun Audio (.au)

      Sun Audio (.au) or Audio/Basic was developed by Sun Microsystems for use

on UNIX systems.

    * Emblaze Audio (.ea)

      Emblaze Audio (.ea) was created by Geo and offers compression similar to

MP3 formats, but its purpose is to be played with a JAVA applet-a miniature

Internet program. Online greeting cards often use JAVA applet programs for

motion and .ea sound files to play music.

Virtual MIDI Keyboard http://www.granucon.com/vmk.html

How do computers use MIDI files?

Sound cards typically employ two methods of sound generation. The main source

are PCM type recordings (like *.WAV files on PC's). These are actually digital

recordings, like the ones your CD player reads when playing a Compact Disk on

your stereo system. While impressive to hear, these files use about 10

Megabytes/minute to produce stereo sound. These can use up quite a bit of hard

drive real estate, in a very short period of time.

The second method a sound card uses to produce sound is on a built-in

synthesizer. Music is played when a MIDI file triggers the sounds on the

synthesizer. These MIDI files are small, and require very little storage space

(a few kilobytes vs. a CD's 30 megabytes for a 3-minute song). As you can see,

CD music files requires THOUSANDS of times more disc space for the same song.

While little space is required for the same song, most lower end sound cards

employ a cheesy-sounding FM synthesizer. We've all heard those FM synthesizers

when hearing tunes on those electronic holiday cards or when we are put on hold

at some places. They sound kinda like cheap electronic bells.

What is "Wavetable" synthesis?

Higher end Sound cards (such as SoundBlaster AWE, Ensoniq Soundscape or Roland

RAP-10) employ a different method of synthesis called "Wavetable" synthesis. The

sound quality of most wavetable Sound cards is significantly better than the

FM-based cards. Wavetable synthesizers use actual "digital samples" of real

musical instruments, to generate music. These are real, hi-fidelity recordings

of the actual instruments.

When a MIDI file is played through a high quality "Wavetable" sound card, the

sound quality approaches that of an actual CD, but without the storage

requirements. Remember, MIDI files take a fraction of the space required by

audio (CD type) files.

What is General MIDI?

General MIDI (referred to as GM from here on out) was developed in the past 5

years and is the basis for "Wavetable" synthesis. GM is actually a set of 120

standard sounds, plus drum kit definitions. All "Wavetable" synthesizers and

Sound cards use the GM soundset to assure compatibility between the

manufacturers.

GENERAL MIDI INSTRUMENTS

(groups sounds into sixteen families, w/8 instruments in each family)

Prog#     Instrument               Prog#     Instrument

(1-8        PIANO)                   (9-16      CHROM PERCUSSION)

1         Acoustic Grand             9        Celesta

2         Bright Acoustic            10        Glockenspiel

3         Electric Grand             11        Music Box

4         Honky-Tonk                12        Vibraphone

5         Electric Piano 1           13        Marimba

6         Electric Piano 2           14        Xylophone

7         Harpsichord                15        Tubular Bells

8         Clav                           16        Dulcimer

   (17-24      ORGAN)                  (25-32      GUITAR)

17        Drawbar Organ               25        Acoustic Guitar(nylon)

18        Percussive Organ            26        Acoustic Guitar(steel)

19        Rock Organ                    27        Electric Guitar(jazz)

20        Church Organ                 28        Electric Guitar(clean)

21        Reed Organ                    29        Electric Guitar(muted)

22        Accoridan                       30        Overdriven Guitar

23        Harmonica                      31        Distortion Guitar

24        Tango Accordian             32        Guitar Harmonics

  (33-40      BASS)                     (41-48     STRINGS)

33        Acoustic Bass                  41        Violin

34        Electric Bass(finger)         42        Viola

35        Electric Bass(pick)           43        Cello

36        Fretless Bass                  44        Contrabass

37        Slap Bass 1                     45        Tremolo Strings

38        Slap Bass 2                     46        Pizzicato Strings

39        Synth Bass 1                   47        Orchestral Strings

40        Synth Bass 2                   48        Timpani

   (49-56     ENSEMBLE)            (57-64      BRASS)

49        String Ensemble 1            57        Trumpet

50        String Ensemble 2            58        Trombone

51        SynthStrings 1                  59        Tuba

52        SynthStrings 2                  60        Muted Trumpet

53        Choir Aahs                       61        French Horn

54        Voice Oohs                      62        Brass Section

55        Synth Voice                      63        SynthBrass 1

56        Orchestra Hit                    64        SynthBrass 2

   (65-72      REED)               (73-80      PIPE)

65        Soprano Sax                73        Piccolo

66        Alto Sax                       74        Flute

67        Tenor Sax                    75        Recorder

68        Baritone Sax                76        Pan Flute

69        Oboe                           77        Blown Bottle

70        English Horn                 78        Skakuhachi

71        Bassoon                       79        Whistle

72        Clarinet                        80        Ocarina

   (81-88      SYNTH LEAD)       (89-96      SYNTH PAD)

81        Lead 1 (square)                89        Pad 1 (new age)

82        Lead 2 (sawtooth)            90        Pad 2 (warm)

83        Lead 3 (calliope)               91        Pad 3 (polysynth)

84        Lead 4 (chiff)                    92        Pad 4 (choir)

85        Lead 5 (charang)              93        Pad 5 (bowed)

86        Lead 6 (voice)                  94        Pad 6 (metallic)

87        Lead 7 (fifths)                   95        Pad 7 (halo)

88        Lead 8 (bass+lead)           96        Pad 8 (sweep)

   (97-104     SYNTH EFFECTS)         (105-112     ETHNIC)

 97        FX 1 (rain)                                105       Sitar

 98        FX 2 (soundtrack)                     106       Banjo

 99        FX 3 (crystal)                           107       Shamisen

100        FX 4 (atmosphere)                  108       Koto

101        FX 5 (brightness)                     109       Kalimba

102        FX 6 (goblins)                         110       Bagpipe

103        FX 7 (echoes)                         111       Fiddle

104        FX 8 (sci-fi)                             112       Shanai

   (113-120    PERCUSSIVE)                  (121-128     SOUND EFFECTS)

113        Tinkle Bell                           121       Guitar Fret Noise

114        Agogo                                122       Breath Noise

115        Steel Drums                       123       Seashore

116        Woodblock                         124       Bird Tweet

117        Taiko Drum                        125       Telephone Ring

118        Melodic Tom                      126       Helicopter

119        Synth Drum                        127       Applause

120        Reverse Cymbal                 128       Gunshot

General MIDI Percussion Key Map

(assigns drum sounds to note numbers. MIDI Channel 10 is for percussion)

To avoid concerns with channels, GM restricts percussion to MIDI Channel 10.

Theoretically, the lower nine channels are for the instruments, but the GM spec

states that a sound module must respond to all sixteen MIDI channels, with

dynamic voice allocation and a minimum of 24 voices.

MIDI   Drum Sound                         MIDI    Drum Sound

Key                                                   Key

35     Acoustic Bass Drum                 59      Ride Cymbal 2

36     Bass Drum 1                            60      Hi Bongo

37     Side Stick                                61      Low Bongo

38     Acoustic Snare                        62      Mute Hi Conga

39     Hand Clap                               63      Open Hi Conga

40     Electric Snare                          64      Low Conga

41     Low Floor Tom                        65      High Timbale

42     Closed Hi-Hat                          66      Low Timbale

43     High Floor Tom                        67      High Agogo

44     Pedal Hi-Hat                            68      Low Agogo

45     Low Tom                                 69      Cabasa

46     Open Hi-Hat                           70      Maracas

47     Low-Mid Tom                         71      Short Whistle

48     Hi-Mid Tom                            72      Long Whistle

49     Crash Cymbal 1                     73      Short Guiro

50     High Tom                               74      Long Guiro

51     Ride Cymbal 1                       75      Claves

52     Chinese Cymbal                     76      Hi Wood Block

53     Ride Bell                                77      Low Wood Block

54     Tambourine                            78      Mute Cuica

55     Splash Cymbal                        79      Open Cuica

56     Cowbell                                  80      Mute Triangle

57     Crash Cymbal 2                      81      Open Triangle

58     Vibraslap