Create a new version of paste:

local function Button(
                                width,
                                height,
                                label,
                                backgroundColorNormal,                                
                                backgroundColorPressed,
                                textColorNormal,
                                textColorPressed,
                                hasBorder,
                                borderColorNormal,
                                borderColorPressed,
                                startColumn,
                                startRow,
                                isPressed,
                                defaultBackgroundColor,
                                defaultTextColor
                            )
    local button = {}
    button.height=height or 1
    button.width=width or 1
    button.label=label or ""
    button.backgroundColorNormal=backgroundColorNormal or colors.black
    button.backgroundColorPressed=backgroundColorPressed or colors.white
    button.textColorNormal=textColorNormal or colors.white
    button.textColorPressed=textColorPressed or colors.black
    button.hasBorder = hasBorder or false
    button.borderColorNormal = borderColorNormal or backGroundColorNormal
    button.borderColorPressed = borderColorPressed or backGroundColorPressed
    button.defaultBackgroundColor = defaultBackgroundColor or colors.black
    button.defaultTextColor = defaultTextColor or colors.white
    button.startColumn = startColumn or 1
    button.startRow = startRow or 1
    button.isPressed=isPressed or false
    function button.press()
        button.isPressed = not button.isPressed
    end
    function button.clicked(column,row)
      return (column >= button.startColumn and column < button.startColumn + button.width and row >= button.startRow and row < button.startRow + button.height)
    end
    function button.draw(display,isPressed,startColumn,startRow)
 
        button.startColumn = startColumn or button.startColumn
        button.startRow = startRow or button.startRow
        display = display or term
        if isPressed == false or isPressed then
            button.isPressed = isPressed
        else isPressed = button.isPressed
        end
        local width = button.width
        local height = button.height
        startRow = button.startRow
        startColumn = button.startColumn
 
        local label = button.label
        local labelPad = 2
 
        -- set border params and draw border if hasBorder
        if button.hasBorder == true then
            -- button must be at least 3x3, if not, make it so
            if width < 3 then
                width = 3
            end
            if height < 3 then
                height = 3
            end
 
            -- set border colors
            if not isPressed then
                if not display.isColor() then
                    display.setBackgroundColor(colors.white)
                else
                    display.setBackgroundColor(button.borderColorNormal)
                end
            else
                if not display.isColor() then
                    display.setBackgroundColor(colors.white)
                else
                    display.setBackgroundColor(button.borderColorPressed)
                end
            end
 
            -- draw button border (inset)
            display.setCursorPos(startColumn,startRow)
            display.write(string.rep(" ",width))
            for row = 2,height-1 do
                display.setCursorPos(startColumn,button.startRow+row -1)
                display.write(" ")
                display.setCursorPos(startColumn+width -1 ,startRow + row-1)
                display.write(" ")
            end
            display.setCursorPos(startColumn,startRow+height-1)
            display.write(string.rep(" ",width))
 
            -- reset startColumn,startRow,width,column to inset button and label
            startColumn=startColumn+1
            startRow = startRow +1
            width = width - 2
            height = height - 2
        end
 
        --set button background and text colors
        if not isPressed then
            if not display.isColor() then
                display.setBackgroundColor(colors.black)
                display.setTextColor(colors.white)
            else
                display.setBackgroundColor(button.backgroundColorNormal)
                display.setTextColor(button.textColorNormal)
            end
        else
            if not display.isColor() then
                display.setBackgroundColor(colors.white)
                display.setTextColor(colors.black)
            else
                display.setBackgroundColor(button.backgroundColorPressed)
                display.setTextColor(button.textColorPressed)
            end
        end
 
        -- draw button background (will be inside border if there is one)
        for row = 1,height do
            --print(tostring(startColumn)..","..tostring(startRow-row))
            display.setCursorPos(startColumn,startRow + row -1)
            display.write(string.rep(" ",width))
        end
 
        -- prepare label, truncate label if necessary
 
        -- prepare label, truncate label if necessary
        if width < 3 then
            labelPad = 0
        end
        if #label > width - labelPad then
            label = label:sub(1,width - labelPad)
        end
 
        -- draw label
        display.setCursorPos(startColumn + math.floor((width - #label)/2),startRow + math.floor((height-1)/2))
        display.write(label)
        display.setBackgroundColor(button.defaultBackgroundColor)
        display.setTextColor(button.defaultTextColor)
    end
    button.toggle = function ()
            button.isPressed = not button.isPressed
            return button.isPressed
        end            
    return button
end
 
function tablelength(T)
  local count = 0
  for _ in pairs(T) do count = count + 1 end
  return count
end
 
function drawSongs()
songNameButtons = {}
    for i,song in ipairs(songNames) do
      -- First check if its on our page
      local lowestSong = currentPage * songsPerPage -- So 0 on page 0, we can use hard > which means the lowestSong+songsPerPage is included on this page and not the next one
      if i > lowestSong and i <= lowestSong + songsPerPage then
     
          if currentSong == i then
            songNameButtons[i] = Button(40,1,song,colors.white,colors.white,colors.black,colors.green,false,colors.white,colors.black,0,i%songsPerPage,false,nil,nil)
          else
            songNameButtons[i] = Button(40,1,song,colors.black,colors.white,colors.orange,colors.green,false,colors.black,colors.black,0,i%songsPerPage,false,nil,nil)
          end
          songNameButtons[i].draw(monitor1)
      end
    end
end
 
function drawScreen(monitor, screenIndex)
    monitor.clear()
   
    if screenIndex == 0 then
        drawSongs()
        left.draw(monitor)
        right.draw(monitor)
        bottom.draw(monitor)
        instrumentsButton.label = "Setup"
        instrumentsButton.draw(monitor)
        pageLabel.label = "Page " .. (currentPage+1) .. "/" .. maxPage
        pageLabel.draw(monitor)
    elseif screenIndex == 1 then
        left.draw(monitor)
        right.draw(monitor)
        bottom.draw(monitor)
        instrumentsButton.label = "Save"
        instrumentsButton.draw(monitor)
        -- Draw the current song title at the top
        monitor.setBackgroundColor(colors.white)
        monitor.setTextColor(colors.black)
        monitor.setCursorPos(1,1)
        monitor.write(songNames[currentSong])
       
        -- So we need to build a list of instruments
        -- And put the value beside each one
        -- And have < and > buttons beside each value to change it
        monitor.setBackgroundColor(colors.black)
        monitor.setTextColor(colors.white)
        for i,name in pairs(varNames) do
            monitor.setCursorPos(1,i+2)
            monitor.write(name)
        end
        instrumentLeftButtons = {}
        instrumentRightButtons = {}
        for i,name in pairs(varValues) do
            monitor.setCursorPos(30,i+2)
            monitor.write(name)
            instrumentLeftButtons[i] = Button(1,1,"<",colors.black,colors.white,colors.orange,colors.green,false,colors.black,colors.black,29,i+2,false,nil,nil)
            instrumentRightButtons[i] = Button(1,1,">",colors.black,colors.white,colors.orange,colors.green,false,colors.black,colors.black,38,i+2,false,nil,nil)
            instrumentLeftButtons[i].draw(monitor)
            instrumentRightButtons[i].draw(monitor)
            -- We should also set instrumentIndex; this represents what position in the instruments list the current variable is
            for j,k in pairs(instruments) do
                if string.lower(k) == string.lower(name) then
                    instrumentIndex[i] = j
                    break
                end
            end
            if instrumentIndex[i] == nil then
                write("Error: Could not find instrument " .. name)
            end
        end
    end
end
 
function saveData()
    -- Using songNames[currentSong], saves a file with that name
    -- Writes serialized varNames and varValues
    local writer = fs.open(songs[currentSong], "w")
    -- The data really should stay like this but too late now...
    -- I want to crunch it into one array
    -- ... But I can't do that because then I can't guarantee the order
    writer.writeLine(textutils.serialize(varNames))
    writer.close()
    writer = fs.open(songs[currentSong] .. "1", "w")
    writer.writeLine(textutils.serialize(varValues))
    writer.close()
end
 
function readData()
    -- Using songNames[currentSong], reads a file with that name
    -- Reads serialized varNames and varValues
    if(fs.exists(songs[currentSong]) and fs.exists(songs[currentSong] .. "1")) then
        varNames = {}
        varValues = {}
        local reader = fs.open(songs[currentSong], "r")
        varNames = textutils.unserialize(reader.readAll())
        reader.close()
        reader = fs.open(songs[currentSong] .. "1", "r")
        varValues = textutils.unserialize(reader.readAll())
        return true
    end
    return false
end
 
function changeToNewSong(toggleOnly)
    -- Using currentSong, sends a Stop request if playing, then Starts a new song
    if playing then
        playing = false
        rednet.send(targetid,"stop")
        if toggleOnly then
            return
        end
    end
    playing = true
    rednet.send(targetid,songs[currentSong])
    -- Directly wait for the responses, there should be two arrays sent back
    local id,msg = rednet.receive(1) -- Max out at 1 second tho, just in case
    local tempNames = textutils.unserialize(msg)
    local id,msg = rednet.receive(1)
    local tempValues = textutils.unserialize(msg)
    if readData() then -- Check if we have saved values
        if tempValues ~= varValues then
            for i,v in pairs(varValues) do
                if(v ~= tempValues[i]) then
                    rednet.send(id,"changeinstrument:" .. tempNames[i] .. ":" .. v)
                end
            end
        end
    else
        -- We had no data, so store what they gave us
        varNames = tempNames
        varValues = tempValues
    end
end
 
--  Start of test Program
 
instrumentIndex = {} -- Contains the index of the instruments list that is currently selected
 
instrumentLeftButtons = {}
instrumentRightButtons = {} -- Indexed by the variable it would adjust
 
varNames = {}
varValues = {}
 
monitor1 = peripheral.wrap("top")
screenNum = 0 -- Indicates what to display on screen
 
left= Button(4,3,"<<",colors.green,colors.red,colors.black,colors.yellow,true,colors.gray,colors.pink,1,30,false,nil,nil)
right = Button(4,3,">>",colors.green,colors.red,colors.black,colors.yellow,true,colors.gray,colors.pink,36,30,false,nil,nil)
bottom = Button(29,3,"Play",colors.lime,colors.red,colors.black,colors.yellow,true,colors.gray,colors.pink,6,30,false,nil,nil)
 
pageLabel = Button(40,1,"Page 1/1",colors.black,colors.black,colors.orange,colors.orange,false,colors.orange,colors.orange,1,29,false,nil,nil)
 
instrumentsButton = Button(40,1,"Setup",colors.orange,colors.red,colors.black,colors.lime,false,colors.orange,colors.pink,1,33,false,nil,nil)
 
songs = {"Megalovania"}
songNames = {"Undertale - Megalovania"}
 
instruments = {"Harp","Bass","Pling","Bell","Chime","Flute","Guitar","Xylophone","BaseDrum","Hat","Snare"}
 
songNameButtons = {}
 
currentSong = 1
currentPage = 0
songsPerPage = 27
 
maxPage = math.ceil(tablelength(songNames)/songsPerPage)
 
-- Display buttons on monitor1
 
-- And text I guess
 
drawScreen(monitor1,screenNum)
 
 
rednet.open("right")
targetid = 0
 
playing = false
 
-- this is our event loop
while true do
  event ={os.pullEvent()}
  -- Check for signal to go to next song
  if playing and event[1] =="rednet_message" then
     if event[3] == "done" and playing then
          currentSong = currentSong + 1
          if currentSong > tablelength(songNames) then
            currentSong = 1
          end
          changeToNewSong()
          drawScreen(monitor1,screenNum)
      end
  end
  if event[1] =="monitor_touch" then
    if left.clicked(event[3],event[4]) then
      currentPage = currentPage - 1
      if currentPage < 0 then
        currentPage = maxPage-1
      end
    elseif right.clicked(event[3],event[4]) then
      currentPage = currentPage + 1
      if currentPage >= maxPage then
       currentPage = 0
      end
    elseif bottom.clicked(event[3],event[4]) then
        changeToNewSong(true) -- Plays or stops as appropriate
    elseif instrumentsButton.clicked(event[3],event[4]) then
        -- Swap screens...
        if screenNum == 0 then
            screenNum = 1
        elseif screenNum == 1 then
            screenNum = 0
            -- Save our song data
            saveData()
        end
       -- drawScreen(monitor1,screenNum)
    elseif screenNum == 1 then
        for i,v in pairs(instrumentLeftButtons) do
            if(v.clicked(event[3],event[4])) then
                -- Cycle 1 instrument left for this index and send rednet command to change it
                instrumentIndex[i] = instrumentIndex[i]-1
                if instrumentIndex[i] <= 0 then
                    instrumentIndex[i] = tablelength(instruments)
                end
                varValues[i] = instruments[instrumentIndex[i]]
                rednet.send(targetid,"changeinstrument:" .. varNames[i] .. ":" .. varValues[i])
                break
            end
        end
        for i,v in pairs(instrumentRightButtons) do
            if(v.clicked(event[3],event[4])) then
                -- Cycle 1 instrument right for this index and send rednet command to change it
                instrumentIndex[i] = instrumentIndex[i]+1
                if instrumentIndex[i] > tablelength(instruments) then
                    instrumentIndex[i] = 1
                end
                varValues[i] = instruments[instrumentIndex[i]]
                rednet.send(targetid,"changeinstrument:" .. varNames[i] .. ":" .. varValues[i])
                break
            end
        end
    else
        for i,v in pairs(songNameButtons) do
            if(v.clicked(event[3],event[4])) then
                -- Set the selected index to this index and do play things
                currentSong = i
                if playing then changeToNewSong() end
                break
            end
        end
   
    end
    -- Redraw songs
    drawScreen(monitor1,screenNum)
   
  end
end