audio
Audio, the synthesis (in whichever way) of sound.
Chromatic scale
- each key/fret is a semitone
- 12 semitones is a full octave
- 2 semitones is a tone
- each scale is made up of patterns of tones and semitones
In order to change the tune with the web audio api do: ```js const osc = ctx.createOscillator()-3 -1 1 4 6 9 11 -4 -2 0 2 3 5 7 8 10 12 .___________________________________________________________________________. : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | : : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | : : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | : <-: |_| | |_| |_| | |_| |_| |_| | |_| |_| | |_| |_| |_| | |_| |_| :-> : | | | | | | | | | | | | | | | | | | : : A | B | C | D | E | F | G | A | B | C | D | E | F | G | A | B | C | D | E : :___|___|___|___|___|___|___|___|___|___|___|___|___|___|___|___|___|___|___: ^ ^ ^ ^ ^ 220 Hz 440 Hz 523.25 Hz 880 Hz 1174.65 Hz (-1 Octave) (middle A) (+1 Octave)
osc.type = 'sawtooth' osc.frequency.value = 440 osc.detune.value = 3 * 100
## Scale
A scale is a collection of notes. A key + a scale pattern is a scale.
- [scales](http://www.gosk.com/chords/m7-chords-for-guitar.php)
## Scale patterns
No matter what note you start on, if you play a pattern you'll get a scale. A
`|` denotes a tone (full jump, 2 frets). A `.` denotes a semitone (half jump, 1
fret). Each of the 7 classic scale patterns is a transposition of the previous
one.
```txt
||.|||. [ ionian (typical major) ]
|.|||.| [ dorian (minor) ]
.|||.|| [ phrygian (minor) ]
|||.||. [ lydian (major) ]
||.||.| [ mixolydian (major) ]
|.||.|| [ aeolian (typical minor) ]
.||.||| [ locrian (minor) ]
Scale patterns determine the key signature. There are more patterns, but these are the major ones. Each scale pattern has their own sounds and characteristics, for example the aeolian is a classic minor scale, the phrygian is a Spanish sounding scale and dorian is often used in folk music.
The third note of a scale pattern signals if it's a major or minor (only 2 possible positions for the third note).
Because each of the 7 classical patterns is a transposition of the previous one, if you start a mode on the next key in the previous mode's scale you get the same notes. The ionian A (A major) has the same notes as the dorian B, as the phrygian C#:
a b c# d e f# g# a (ionian mode)
b c# d e f# g# a b (dorian mode)
c# d e f# g# a b c# (phrygian mode)
chords
Building a chord:
- determine key
- determine scale pattern
1 3 5 triad (major / minor) (3 determines)
1 3 5 7 seventh (major / minor / diminished) (3 / 7 determine)
triad
- A triad is a chord with 3 notes.
1 3 5of the key you are playing in
Filters
Filters can modify values. Using .connect() they are analogous to through
streams for audio.
const f = audioContext.createBiquadFilter()
f.type = 'highpass'
f.frequency.value = 10000
f.connect(ctx.destination)
filter types
lowpass only values lower
highpass only values higher
bandpass only values in range
lowshelf
highshelf
peaking
notch
allpass
envelopes
Envelopes wrap sounds and smear them over time.
attack envelope
Attack envelopes ramp up the value.
const attack = audioContext.createGain()
attack.gain.value = 0
attack.gain.setTargetAtTime(1, startTime, 0.1)
release envelope
release envelopes decrease the value.
const release = audioContext.createGain()
release.gain.setTargetAtTime(0, endTime, 0.2)
Keep in mind when adding a release envelope, the sound needs to keep playing until the release finishes otherwise it will just stop.
// provide enough time for the exponential falloff
oscillator.stop(endTime + 2)
modulating audio parameters
Modules
- baudio - generate audio streams with functions
- jsynth - Generate audio/DSP with javascript functions in the browser