CODEWITHSUNDEEP
javaalgorithmmididata-conversion
Ellis
Ellis

Reputation: 567

Converting musical note Strings to MIDI pitch number

I have written the following method to convert notes (with the octave appended to the end) to the corresponding MIDI pitch:

// Converts a note string (MUST HAVE OCTAVE) to an integer pitch.
public static int convertToPitch(String note) {
    String sym = "";
    int oct = 0;

    String[] notes = { "C", "Db", "D", "Eb", "E", "F", "Gb", "G", "Ab", "A", "Bb", "B" };

    char[] splitNote = note.toCharArray();

    // If the length is two, then grab the symbol and number.
    // Otherwise, it must be a two-char note.
    if (splitNote.length == 2) {
        sym += splitNote[0];
        oct = splitNote[1];
    } else if (splitNote.length == 3) {
        sym += Character.toString(splitNote[0]);
        sym += Character.toString(splitNote[1]);
        oct = splitNote[2];
    }

    // Find the corresponding note in the array.
    for (int i = 0; i < notes.length; i++) {
        if (notes[i].equals(sym)) {
            return Character.getNumericValue(oct) * 12 + i;
        }
    }

    // If nothing was found, we return -1.
    return -1;
}

And it works just great. However, I would also like to be able to use convertToPitch() with the alternate note value (Db becomes C#, etc.) for each note with an alternate name. Is there a way to do this without tearing my method apart?

Upvotes: 0

Views: 2967

Answers (3)

danzel
danzel

Reputation: 413

You can handle the accidentals separately. So with the least modification of your code:

[...]
String sym = "";
int oct = 0;
int accidental = 0; // initialize with default value 0 (i.e. no accidental)

[...]

} else if (splitNote.length == 3) {
    sym += Character.toString(splitNote[0]);
    switch (splitNote[1]){
        case '#':
            accidental = 1;
            break;
        case 'b':
            accidental = -1;
            break;
        default:
            return -1; // you should really use Exceptions instead
    }
    // don't concat accidental to sym
    oct = splitNote[2];

[...]

        return Character.getNumericValue(oct) * 12 + i + accidental; // !! read the documentation of Character#getNumericValue !!
[...]

However, using the array index as a mapping isn't the best approach in my opinion. Depending on your input format this doesn't work since Cb is a valid note but there is no array index -1. You could create a Map<String,Integer> (like "C" is mapped to 0, "D" to 2, etc.) or use an enumeration. You should also use Exceptions instead of returning -1; this way you can differentiate between a malformatted string ("abbc123") and a value out of range ("B#9").
Finally, If I remember correctly, there is an offset in MIDI pitch (like C0 isn't 0 but 12).

Upvotes: 0

gpasch
gpasch

Reputation: 2672

You could do it like this

public static int convertToPitch(String note) {
  String sym = "";
  int oct = 0;
  String[][] notes = { {"C"}, {"Db", "C#"}, {"D"}, {"Eb", "D#"}, {"E"},
    {"F"}, {"Gb", "F#"}, {"G"}, {"Ab", "G#"}, {"A"}, {"Bb", "A#"}, {"B"} };

  char[] splitNote = note.toCharArray();

  // If the length is two, then grab the symbol and number.
  // Otherwise, it must be a two-char note.
  if (splitNote.length == 2) {
    sym += splitNote[0];
    oct = splitNote[1];
  } else if (splitNote.length == 3) {
    sym += Character.toString(splitNote[0]);
    sym += Character.toString(splitNote[1]);
    oct = splitNote[2];
  }

  // Find the corresponding note in the array.
  for (int i = 0; i < notes.length; i++)
  for (int j = 0; j < notes[i].length; j++) {
    if (notes[i][j].equals(sym)) {
        return Character.getNumericValue(oct) * 12 + i;
    }
  }

  // If nothing was found, we return -1.
  return -1;
}

Upvotes: 1

Sason Ohanian
Sason Ohanian

Reputation: 785

You could maybe begin by "normalizing" input note to expected input. I.e. initialize a string -> string map with all possible notes and normalized mappings. Should only result in some map initialization in constructor and call to map method in the beginning of convertToPitch.

Upvotes: 2

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