Synthesizer Prototype 2 - A synthesizer for an organ without need for any assets. Use the keys 1Q2W3ER5T6YU8I9O0P[=], backspace, \ZSXDCVGBHNM,L.;/, and right shift to play it.

synth.lua

--[[
PUBLIC DOMAIN
Where this designation is not recognized, you are
permitted to copy, modify, and distribute this code
without restriction.
 
Lucien Greathouse
(LPGhatguy)
]]

local default_samples = 48000 --Sample rate in hertz
local pitch_rate = 2^(1 / 12) --The base to use for producing tones
local pitch_offset = -12 --Tone offset in semitones (12 is one octave)

local function round(n)
	return math.floor(n + 0.5)
end

local function hertz(semitones, base)
	base = base or 220
	return base * pitch_rate ^ (semitones + pitch_offset)
end

local function build_tone(frequencies, samples)
	samples = samples or default_samples

	local data = love.sound.newSoundData(samples, samples, 16, 1)
	local scalars = {}

	for index = 1, #frequencies do
		local frequency, amplitude

		if (type(frequencies[index]) == "table") then
			frequency = frequencies[index][1]
			amplitude = frequencies[index][2] or 1
		else
			frequency = frequencies[index]
			amplitude = 1
		end

		scalars[index] = {math.floor(frequency + 0.5) * math.pi * 2 / samples, amplitude}
	end

	for pos = 0, samples - 1 do
		local sum = 0

		for index = 1, #scalars do
			sum = sum + (scalars[index][2] * math.sin(pos * scalars[index][1]))
		end

		data:setSample(pos, math.min(1, math.max(-1, sum / #frequencies)))
	end

	local wrapper = love.audio.newSource(data)
	wrapper:setLooping(true)

	return wrapper
end

local tones = {}
local fading = {}

local keys = {
	["1"] = -13,
	q = -12,
	["2"] = -11,
	w = -10,
	["3"] = -9,
	e = -8,
	r = -7,
	["5"] = -6,
	t = -5,
	["6"] = -4,
	y = -3,
	u = -2,
	["8"] = -1,
	i = 0,
	["9"] = 1,
	o = 2,
	["0"] = 3,
	p = 4,
	["["] = 5,
	["="] = 6,
	["]"] = 7,
	["backspace"] = 8,
	["\\"] = 9,

	z = 5,
	s = 6,
	x = 7,
	d = 8,
	c = 9,
	v = 10,
	g = 11,
	b = 12,
	h = 13,
	n = 14,
	j = 15,
	m = 16,
	[","] = 17,
	l = 18,
	["."] = 19,
	[";"] = 20,
	["/"] = 21,
	["rshift"] = 22
}

function love.update(delta)
	for key, value in pairs(fading) do
		value:setVolume(math.max(0, value:getVolume() - delta * 1.3))

		if (value:getVolume() <= 0) then
			value:stop()
		end
	end
end

function love.keypressed(key)
	if (keys[key]) then
		local semitones = keys[key]

		if (not tones[semitones]) then
			tones[semitones] = build_tone({
				{hertz(semitones), 1},
				{hertz(semitones + 12), 0.937},
				{hertz(semitones + 19), 0.960},
				{hertz(semitones + 24), 0.863},
				{hertz(semitones + 28), 0.889},
				{hertz(semitones + 31), 0.789}
			}, 48000)
		end

		if (fading[semitones]) then
			fading[semitones] = nil
		end

		--tones[semitones]:stop()
		tones[semitones]:setVolume(0.5)
		tones[semitones]:play()
	end
end

function love.keyreleased(key)
	if (keys[key]) then
		local semitones = keys[key]

		if (tones[semitones]) then
			fading[semitones] = tones[semitones]
		end
	end
end