Play music in Codea / Codify

PlayMusic.lua

-- Play Music.  This plays polyphonically, using the draw function and a frame counter for timing.
-- By Fred.

-- Use this function to perform your initial setup
function setup()
    
    -- initialise variables and clear screen
    frame = 0
    measure = 1
    tuneLength = 0
    background(0, 0, 0, 0)
    
    -- This slidable parameter adjusts the number of frames between musical measures.
    -- It controls the speed of the music.
    iparameter("pauseAmount",0,100,10)
    
    -- These are the names of the notes and their (trial and error) equivalent seed numbers 
    -- for the sound() function.  The digit tells us which octave it is.
    -- Further mapping of the seed address space would expand our range and improve tonal quality.
    notes = {b2=118,c3=85,d3=321,e3=48,f3=63,g3=60,a3=68,b3=11,c4=84}
    
    -- This is the tune we want to play, in a multidimensional array.
    -- Each element of the table is a table of what notes should be played for each
    -- sequential measure.  This allows chords, and rests as an empty table.
    -- Minuet in G by JS Bach (transposed to C)
    tune={{"c3","e3","g3"},{},{"c3"},{"d3"},{"e3"},{"f3"},{"c3","e3","g3"},{},{"c3"},{},{"c3"},{},{"c3","f3","a3"},{},{"f3"},{"g3"},{"a3"},{"b3"},{"c3","e3","g3","c4"},{},{"c3"},{},{"c3"},{},{"b2","d3","f3"},{},{"g3"},{"f3"},{"e3"},{"d3"},{"c3","e3"},{},{"f3"},{"e3"},{"d3"},{"c3"},{"b2","d3"},{},{"c3","e3"},{"d3"},{"c3"},{"b2"},{"c3"}}

    
    -- List the notes available and their assigned seeds
    print("These are the notes and sound() seeds.")
    for key, value in pairs(notes) do
        print("notes."..key.." = "..value) 
    end
    
    -- Count the length of the tune so that later we don't crash at the end.
    for key, value in pairs(tune) do
        tuneLength = tuneLength + 1
    end
end

-- This function gets called once every frame
function draw()
    
    -- If the number of frames specified by the pauseAmount slider has passed, we play the next
    -- element in the tune table.  This is the next musical measure.  This works better than
    -- trying implement a pause function that holds up the whole program.
    if frame % pauseAmount == 0 and measure <= tuneLength then
        readMusic()
        
        -- Reset frame counter rather than going to infinity and beyond.
        frame = 0
    end
    frame = frame + 1
end

-- Start the music again if touched.
function touched(touch)
    if CurrentTouch.state == BEGAN then
        measure = 1
    end
end

function readMusic()
    
    -- Based on the current measure count, find the table of notes to be played now from the
    -- tune table. Because we are using pairs, the notes making up this chord will not
    -- necessarily be played in order, but it's pretty quick.
    for key, value in pairs(tune[measure]) do
                
        -- The seed given here to the sound() function determines the pseudorandom
        -- qualities of the sound.  The notes table approximates the notes of a scale
        -- with certain seed numbers.  Your listening mileage may vary.
        sound(SOUND_BLIT,notes[value])
    end
        
    -- Increment our measure count so next time we play the following measure of music.
    measure = measure + 1
end