notes.txt

Wanted Feature List / Change List
---------------------------------
Algorithms on Other Systems (to consider)
	1 -> 2 & 3 -> 4		(Bleass, Dirtywave M8, Ableton) diamond shape
	1 -> 2 -> 3 & 4		(Bleass, Dirtywave M8, Ableton)
	1 & 2 & 3 -> 4			(DX7, Bleass, Dirtywave M8, Ableton)
	1 -> 2 & 3, 4			(DX7, Dirtywave M8, Ableton)
	1->2&4, 3->2&4			Algorithm 4 + more (Digitone)
	1->2&3, 2->3->4		(Digitone)
	1 -> 2 -> 4, 3 -> 4	(Ableton)
Then renumber Operator 2 and Operator 3 (switch around)?
	Affects ym2612.js

Distortion (symmetry) modulation?

Timbre frames
	Replace the basic wave shapes with a weighted sum (or difference) of saws, pulse waves and triangles at different frequency multiples? (+ one custom wave or sine with only 0 & 180 degree phases)
		E.g. Saw at 1f sets the overall shape, saw at 2f modifies the even numbered harmonics
		i.e. layered timbre frames:
		Sawtooth wave: frequencies: n * m, amplitudes: 1/n, alternating phases
		Square wave: frequencies: (2n-1) * m, amplitudes: 1/(2n-1), equal phases
		Triangle wave: frequencies: (2n-1) * m, amplitudes: 1/(2n-1)^2, alternating phases
		n is a positive integer
		Optionally AM or ring mod a basic shape with a sine wave
		Pass the wave (or combined sum?) though a LP filter (with resonance?) (HP filter available too?)
	Take account of operator ratio / fixed frequency when calculating timings
	Reuse all oscillators when adjacent frames only vary in amplitude (or pitch ratio if fading between pitches) (eliminates the need to adjust timing to align the waveforms)
	Change sampling interval to approximately every 4 semitones (see spreadsheet)
	Option to set start time
		particularly useful for skipping hold time of first frame on first loop iteration
		round to zero crossing point (specify as frame number + offset?)
	Option to have a bidirectional loop
	Option to set pitch ratio using transpose + detune
	Option to cross fade using cosine shape
	Option to set fade time as a musical interval when timingPitch = 1
	Option to fade out harmonics one by one using a filter
		Filter sweep then volume fade? Or simultaneous? Or overlapping? Or sweep filter down to (near?) 0Hz?
		General case (when combined with FM): arbitrary filter sweep?
			Or only available when not using FM?
	Integrated FM modulator (sine) with DADSR envelope and ratio or fixed (and semi-fixed?)
		Option to only apply it to some of the oscillators
	Option to glide between frequencies
	Release (post loop) frames
	Single cycle waveform samples as frames

	Different sets of timbre frames for different note ranges?
	Different sets of timbre frames for different velocities?
	Option to randomize (or key track?) sample start position (by a specified amount?) and direction (with a specified probability)? (Padshop Pro 2)
		Think of it like a free running LFO? (if not truly random but based on time mod something with offset)
	Resynthesis

Phase distortion?
	Fix intersecting blend vectors
	Resonant waves: Don't use absolute value (except for sawtooth where both should be offered)
	Finish implementing playback modes
	Sample starting offsets
	Option to advance wavetable position by changing loop end and start positions using setTimeout
	Option to mix in some fundamental
		Fundamental or source wave if the source is not sinusoidal?
		Fade this signal in gradually to remedy a final zero phase offset
	Option to invert frequency gain
	Too similar to feedback? Instead of feedback?
	Transfer functions
		Half slow, Half fast		(a, 0.5), (1, 1)
			cos(x) -> sawtooth(x)
				Not an exact recipe to emulate feedback
					e.g. when feedback = 5 then more like (0.91, 0.4) ?
		...
		Impulse						x ^ a (or with asymmetry reversed)
		Waveshaper					asin(f(gain * sin(2PI * x))) / 2PI
			In general: apply the virtual input waveform, then the inverse of the actual input
		Wavefolder					n * sin(2PI * x) = FM synthesis with 0Hz carrier

Additive waveforms that replicate feedback?
	Would we still be able to have a feedback envelope?

Option to not reset phase
Let filter go down to 0Hz
Filter key tracking and glide?
Only respond to MIDI when visible/active?
Bug: Reading .value is broken in chrome
Bug: mixPCM doesn't support 2-op channels
Changing channel volume while PCM is in use doesn't work (problem?)

Make envelope diagram dynamic
Add "Key On" and "Key Off" annotations to envelope diagram

tremolo & auto pan phase offset
Bug: feedback strength (when n=7)?
Bug: inconsistent tone (less frequent when soloed)

Option to glide by a fixed number of semitones (better for poly)
	See Pre-Glide on Novation Peak

Dampening phase should only apply when attenuation is < 0x200
When envelope reset is on then keep the beginning of the attack (& hence the phase) synchronized by waiting until all operators have been dampened
	by applying the longest dampening time to all operators?
	delay stage should happen after dampening (but not have rate scaling applied?)
	add initial phase parameter
Sustain on/off envelope option (one shot)
Add second release stage to envelopes (applied from when Operator 1 reaches -18db and then takes effect across operators, see "reverb" in DX11 manual)
AM envelopes
Operator ratio bend
	Separate ratio node (so it works with pitch bend and glide)
Fixed operator with partial key tracking ("frequency key scaling") (as -200..200 with specified centre key) (FM-X & FS1R)
Fixed operator level linked to velocity (FM-X)
Pitch envelope amount linked to velocity
compressor doesn't support soft knee
compressor doesn't work with pre-gain higher than 4
only run lfo when tremolo, vibrato, panbrello, etc. depth is non-zero

linearValueAtTime - check values saved appropriately
Ability to make parameters velocity sensitive (e.g. distortion, filter envelope amount, resonance (FS1R))
ability to add small amount of noise to operators for character?
	E.g. +-1/2048
envelopes synced to tempo?
attenuation bend and velocity?

Noise/S&H/sample as LFO source?
Level scaling (per operator)
	Breakpoint
	Left and right depths (change in output level)
	Left and right curves (+linear, -linear, +exponential, -exponential, +stepped? (OPL style), -stepped)
	Can be applied to filter resonance too

Oscillator phase should reset on each SSG loop for modes 0 and 4
	Non-looping shapes can be looped (via rapid retriggering)
	Oscillator should stay paused until attenuation is < 0x200
	Hard sync effect.
SSG loop should include attack phase (modes 0 and 4) (but it isn't 4x faster)
SSG should only run at 4x speed while attenuation is < 0x200
envelope shift
allow cutting SSG sample short (sync)
allow custom SSG shapes (max 255 levels, otherwise like PSG)

on screen keyboard
	http://www.quadibloc.com/other/cnv05.htm
	147mm and 100mm lengths

LFO centering (only up / only down / bipolar)?

High pass filter?
	Option to have two low pass filters instead?
Wet/Dry control on filter?

PSG
	Write reciprocal worklet.
	Filter for PSG
	separate into multiple files
	overall volume control for patch
	panning (but no modulation)
	glide (no stepping)
	pitch bend
	discrete pitch movements
		bends (sometimes looping) simulating vibrato or envelope
		based on frequency numbers
	looping envelope
	filter envelope
	LFO delay & fade, LFOs per voice, optional key sync (like FM LFO)
	see AY8930 (only use envelope per voice from the enhanced features), Super PSG, maxYMiser & inSIDious for more ideas
	No separate tremolo
		Generalize envelope to support custom shapes
			Use 1: custom envelope shape
			Use 2 (audio rate): custom waveform (oscillator output constant)
			Use 3 (audio rate): AM
			Up to 255 steps
			Each step lasts between 1 frame (1/60 second) and 255 frames
			Up to 31 levels (or 16 when playing at the fastest speed)
			Looping or not
			Rate linked to pitch or not
		Quick options to create tremolo
	new oscillator on each key on? Need to prevent frequency going too low
	noise channel
		option to configure LFSR polynomial and noise bit depth and starting value and repetitions of each sample
		tidy up code
	per channel tunings
	generalize getMIDINote to handle different interval and divisions values
	replace calcKeyCode with less jumpy version

OPL2/3-like features
	Compatibility
		Fast envelope setting (matching OPL clock rate)
		Separate LFOs for pitch and volume?

One operator channels

Setting to let LFO track note frequency at low-ish speeds (pseudo 5th operator)? Why only low?
	Settings: octave(?) and detune
	Montage OS v3 goes up to 1356.59Hz

Amplitude Bend
	How will it work with 2-op channels?
	Repeating via SSG

Filter envelope
	Can be inverted
	Velocity can affect attack rate

Looping bends?

Delay/Chorus unit

WAV output

Combine sample with synth
	50ms limit for a transient?
	Roland Linear Arithmetic Synthesis
	Korg Advanced Integrated synthesis (M1)
	Casio ZPI & Advanced and High Quality Large Waveform
	Ensoniq Cross Wave Synthesis (SQ-80)
	Kawai Digital Multi Spectrum (K4)
	Yamaha SY77, etc.

Samples as operator waveforms
	Only available for an operator that is not modulated by another operator or itself
	Noise?
	Custom waveforms?

makeBasicWaveform
	alternating / invert every x repetitions (see also SY-77 waveforms)
	trapezoid option (as fraction that is flat, increase sine/tri frequency as needed)

Microtuning
	step offsets for PSG
	getMIDINote for PSG

MIDI messages
	sustain
	mod wheel
		assignable to volume, vibrato depth or tremolo depth (any combination, 3 sensitivity controls)
	foot controller (CC4)
		assignable to volume, vibrato depth or tremolo depth
	expression (alters volume) (CC11)
	program change

			Volume Slider
			Pitch Bend
			Mod Wheel	Aftertouch	Foot	Breath
Volume		X							X
Vibrato		X				X			X			X
Tremolo		X				X			X			X
Pitch			X				X						X
EG Bias						X						X

"Performance Play" (from DX11)?
	A performance:
		alternates through instruments in sequence (+detune, transpose, volume, "pan", microtuning on/off) OR
		splits the keyboard by note number (lower bound, upper bound, modulo arithmetic)
Chord playing "chord set"? (DX11)

Panning based on LFO, velocity or note number
Round robin panning

Series: Yamaha DX11, TX81Z, TQ5, YS200, V50

More Ideas
	Velocity sensitive detuning

Customizable damping time?

UI
	Quick edit (DX11 manual p.13), including "tone" (all modulator levels, Ableton) and balance (between outputs, Digitone)
		Ability to map LFO to balance
	Tabindexes in the custom algorithm section
	Warn user when attempting to apply an LFO effect and the LFO's frequency is zero.
	2 op / 4 op selector UI
	Use slider to control coarse and fine (detune2) ratios together
	Pad LED display with trailing zeros after decimal point
	More intense red LEDs

initial phase offsets (DX7)("Understanding FM Implementations: A Call for Common Standards")
	carrier:modulator	modulator	carrier
			1:1			PI				0
			1:2			0				0
			1:3			PI				0
			2:3			PI				PI
			2:1			0				PI