download generated sequence as midi file

elm-package.json

@@ -10,7 +10,9 @@
     "dependencies": {
         "elm-community/random-extra": "2.0.0 <= v < 3.0.0",
         "elm-lang/core": "5.0.0 <= v < 6.0.0",
-        "elm-lang/html": "2.0.0 <= v < 3.0.0"
+        "elm-lang/html": "2.0.0 <= v < 3.0.0",
+        "newlandsvalley/elm-binary-base64": "1.0.2 <= v < 2.0.0",
+        "newlandsvalley/elm-comidi": "3.0.0 <= v < 4.0.0"
     },
     "elm-version": "0.18.0 <= v < 0.19.0"
 }

src/Main.elm

@@ -1,13 +1,16 @@
 module Main exposing (..)
 
-import Html exposing (Html, text, div, h1, button, p, i)
+import Html exposing (Html, text, div, h1, button, p, i, a)
 import Html.Events exposing (onMouseDown, onMouseUp, onClick)
-import Html.Attributes exposing (class)
+import Html.Attributes exposing (class, href, download, downloadAs)
 import Ports exposing (..)
 import Types exposing (..)
 import Random exposing (generate)
 import Array exposing (Array, fromList, toList, map)
 import Random.Array exposing (shuffle)
+import Midi.Types as Midi
+import Midi.Generate exposing (recording)
+import BinaryBase64 exposing (encode, decode)
 
 
 ---- MODEL ----
@@ -45,10 +48,10 @@ pitchToSampleUrlMapping (Pitch note accidental octave) =
 
 loadPianoSamples : Cmd msg
 loadPianoSamples =
-    [ Pitch C Nothing 4
-    , Pitch D (Just Sharp) 4
-    , Pitch F (Just Sharp) 4
-    , Pitch A Nothing 4
+    [ Pitch C Nothing middleOctave
+    , Pitch D (Just Sharp) middleOctave
+    , Pitch F (Just Sharp) middleOctave
+    , Pitch A Nothing middleOctave
     ]
         |> List.map pitchToSampleUrlMapping
         |> loadSamples
@@ -59,13 +62,36 @@ generate12ToneRow =
     Random.generate RowGenerated (Random.Array.shuffle (chromaticScale 4))
 
 
+flatten : List (List a) -> List a
+flatten list =
+    List.foldr (++) [] list
+
+
+zipWithIndex : List a -> List ( a, Int )
+zipWithIndex list =
+    List.range 0 (List.length list) |> List.map2 (,) list
+
+
+toMidi : Array Pitch -> List Midi.Byte
+toMidi row =
+    row
+        |> Array.toList
+        |> List.map toMidiNumber
+        |> zipWithIndex
+        |> List.map
+            (\( midiNumber, i ) ->
+                [ ( 0, Midi.NoteOn 0 midiNumber 64 )
+                , ( 2, Midi.NoteOff 0 midiNumber 0 )
+                ]
+            )
+        |> flatten
+        |> Midi.SingleTrack 4
+        |> recording
+
+
 init : ( Model, Cmd Msg )
 init =
-    let
-        cmd =
-            Cmd.batch [ loadPianoSamples, generate12ToneRow ]
-    in
-        ( Nothing, cmd )
+    ( Nothing, Cmd.batch [ loadPianoSamples, generate12ToneRow ] )
 
 
 
@@ -93,7 +119,7 @@ update msg model =
             ( Just (Stopped row), Cmd.none )
 
         GenerateNew12ToneRow ->
-            ( Nothing, Cmd.batch [ stopSequence (), generate12ToneRow ] )
+            ( model, Cmd.batch [ stopSequence (), generate12ToneRow ] )
 
         TogglePlay ->
             case model of
@@ -128,6 +154,7 @@ rowWithControls row icon =
         , p []
             [ button [ onClick TogglePlay ] [ i [ class icon ] [] ]
             , generateButton
+            , a [ href ("data:audio/midi;base64," ++ (encode (toMidi row))), downloadAs "luigi.midi", class "button" ] [ i [ class "fas fa-download" ] [] ]
             ]
         ]
 

src/Types.elm

@@ -43,6 +43,11 @@ type alias Model =
     Maybe Row
 
 
+middleOctave : Int
+middleOctave =
+    4
+
+
 chromaticScale : Octave -> Array Pitch
 chromaticScale octave =
     Array.fromList
@@ -59,3 +64,50 @@ chromaticScale octave =
         , Pitch A (Just Sharp) octave
         , Pitch B Nothing octave
         ]
+
+
+type alias MidiNumber =
+    Int
+
+
+toMidiNumber : Pitch -> MidiNumber
+toMidiNumber (Pitch letter accidental octave) =
+    (octave + 1) * 12 + (letterToInt letter) + (accidentalToInt accidental)
+
+
+letterToInt : Letter -> Int
+letterToInt letter =
+    case letter of
+        C ->
+            0
+
+        D ->
+            2
+
+        E ->
+            4
+
+        F ->
+            5
+
+        G ->
+            7
+
+        A ->
+            9
+
+        B ->
+            11
+
+
+accidentalToInt : Maybe Accidental -> Int
+accidentalToInt accidental =
+    case accidental of
+        Just Sharp ->
+            1
+
+        Just Flat ->
+            -1
+
+        Nothing ->
+            0

src/index.js

@@ -30,9 +30,10 @@ app.ports.loadSamples.subscribe(function(pitchToSampleUrlMapping){
 
 app.ports.startSequence.subscribe(function(seq){
   var noteLength = "8n"
-  sequence = new Sequence(function(time, note){
+  var subdivision = "8n"
+  sequence = new Sequence(function(_, note){
     sampler.triggerAttackRelease(note, noteLength)
-  }, seq, noteLength);
+  }, seq, subdivision);
   Transport.start()
   sequence.start();
 });

src/main.css

@@ -7,7 +7,7 @@ body {
   color: #DFDFDF;
 }
 
-button {
+button, .button {
   border: 1px solid #666666;
   background-color: #858585;
   user-select: none;

tests/Tests.elm

@@ -2,21 +2,27 @@ module Tests exposing (..)
 
 import Test exposing (..)
 import Expect
+import Types exposing (..)
 
 
 -- Check out http://package.elm-lang.org/packages/elm-community/elm-test/latest to learn more about testing in Elm!
 
-
 all : Test
 all =
-    describe "A Test Suite"
-        [ test "Addition" <|
+    describe "Pitch to MIDI number"
+        [ test "A0 should be 21" <|
+            \_ ->
+                Expect.equal (toMidiNumber (Pitch A Nothing 0)) 21
+        , test "C8 should be 108" <|
+            \_ ->
+                Expect.equal (toMidiNumber (Pitch C Nothing 8)) 108
+        , test "C4 should be 60" <|
             \_ ->
-                Expect.equal 10 (3 + 7)
-        , test "String.left" <|
+                Expect.equal (toMidiNumber (Pitch C Nothing 4)) 60
+        , test "F#5 should be 78" <|
             \_ ->
-                Expect.equal "a" (String.left 1 "abcdefg")
-        , test "This test should fail" <|
+                Expect.equal (toMidiNumber (Pitch F (Just Sharp) 5)) 78
+        , test "F#5 should be 78" <|
             \_ ->
-                Expect.fail "failed as expected!"
+                Expect.equal (toMidiNumber (Pitch F (Just Sharp) 5)) 78
         ]