Make a program the takes 3 notes and builds the possible chords out of the combi

ID: 3905857 • Letter: M

Question

Make a program the takes 3 notes and builds the possible chords out of the combination of the three notes, including the root.

Description:

Most Western music is based on the chromatic scale: a series of 12 pitches, represented as notes, each a semitone apart. Notes are named with the letters A-G. Some notes are named just a letter, while some have a suffix called an “accidental” meaning a semitione above or below the note with the letter-name.

Starting from A, the 12 tones can be named

With #'s

With b' s

Other names

The difference between two successive notes is called a half-step. The order of notes is cyclic. That is, the note one half-step higher than G#/Ab is again A, and the note one half-step lower than A is Ab/G#. Notes that are a multiple of 12 half-steps apart have the same name, and for our purposes we will consider them equivalent.

Each pitch may have multiple names: A# is the same as Bb, C# is the same as Db, etc. The alternate names of a pitch is called an enharmonic.

Intervals

The distance between two notes is called an interval. The names of the intervals are:

Distance in Half-Steps

Name of Interval

Perfect unison

Minor second

Major second

Minor third

Major third

Perfect fourth

Diminished fifth

Perfect fifth

Augmented fifth

Major sixth

Minor seventh

Major seventh

Chords

A chord in music is made of three or more notes that is heard as if sounding simultaneously. A three-note chord, called a triad is named made from a 7-note subset of the chromatic scale, called the diatonic scale. Each note is mapped to each of the letters A-G with potentially an accidental.

Chord Spelling

Chords are “spelled” by identifying the notes. For example

G B D

C Eb G

B D# G

Note: (no pun intended) the note might not be in order, that is, the first note might not be the root of the chord.

Chord Quality

The chord quality is determined by the interval between the root and the third note of the diatonic scale. When the third is 4 semi-tones from the root, it's a major chord; if it is 3 semi-tones, it is a minor chord.

The Altered 5th

The distance between the root and the fifth note of the diatonic scale is normally 7 semi-tones from the root. If the fifth is a semi-tone higher the chord is augmented, if a semi-tone lower, it is diminished.

Chord Name

A chord is named based on

The root note (e.g. “C”)

The chord quality(e.g. major or minor).

The alteration of fifth note of the diatonic scale (e.g. diminished or augmented).

The chord name can be determined two ways:

Method 1: by measuring the interval between the root and third, and then the interval between the third and fifth or,

Method 2: by measuring the interval between the root and third, then the interval between the root and the fifth.

Method 1

Method 2

Root-->Third

Third-->Fifth

Chord Name

Root-->Third

Root-->Fifth

Major third

Minor third

Major (“maj”)

Major third

Perfect fifth

Minor third

Major third

Minor (“min”)

Minor third

Perfect fifth

Major third

Augmented (“aug”)

Major third

Augmented fifth

Minor third

Diminished (“dim”)

Minor third

Diminished fifth

Assignment:

Create a class named ChordFinder with the following features:

Feature

Signature

Requirement

Constructors

N/A

Will be a utility class—with just a static public method

Methods

static Set getChordName(String notes)

Input: Valid input must have exactly three discrete notes separated by whitespace

Accidentals will use “#” for sharp and “b” for flats.

too many or too few notes should throw an IllegalArgumentException

an invalid note, e.g. “Zb”, should throw an IllegalArgumentException

Output: A set that

containing the names of possible chords names of the given notes

The format must be where

is the root note, “A” – “G” optionally followed by a “b” or “#” representing a sharp or flat respectively. The note must be upper-case

a space

is one of “maj”,“min”,“aug”,“dim”; the name must be lower case

Precondition: Notes are recognized (character A-Goptionally followed by a ‘b’ for flats or ‘#’ for sharps).

Note: while double sharps and flats exist, they are not within scope.

Example Test Cases

Scenario

Expected results

getChordName("D G B")

[“G maj”]

Root : G

Interval G-->B : major third

Interval B-->D: minor third

getChordName(“C Eb G” )

[“C min”]

Root: C

Interval C--> Eb : minor third

Interval C--> G : perfect fifth

getChordName(“B D# G”)

[“B aug”, “D# aug”, “G aug”]

Roots : B, D#, or G

Intervals (B—>D#, D#-->G, and G-->B) : major third

Intervals (B-->G , D#-->B, G-->D#) : augmented fifth

With #'s

With b' s

Other names

Explanation / Answer

Answer: See the code below:

----------------------------------------------------------

package cordfinderdemo;

import java.util.HashSet;
import java.util.Set;

/**
* Game class
*
*/
public class CordFinder {

   static String[] tonesWithHash = {"A","A#","B","C","C#","D","D#","E","F","F#","G","G#"};
   static String[] tonesWithB = {"A","Bb","B","C","Db","D","Eb","E","F","Gb","G","Ab"};
   static String[] tonesOtherNames = {"","","Cb","B#","","","","Fb","E#","","",""};
   static String[] intervals = {"Perfect unison","Minor second",
           "Major second","Minor third","Major third","Perfect fourth",
           "Diminished fifth","Perfect fifth","Augmented fifth","Major sixth",
           "Minor seventh","Major seventh"};
   /**
   * getCordName() method
   */
   public static Set getCordName(String notes) {
       Set set = new HashSet();
       //individual notes
       String[] noteTokens = notes.split(" ");
       //check if right number of notes are passed
       if (noteTokens.length < 3 || noteTokens.length > 3)
           throw new IllegalArgumentException("Wrong number of notes");

       return set;
       // TODO Auto-generated constructor stub
   }

   /**
   * @param args
   */
   public static void main(String[] args) {
       // TODO Auto-generated method stub
       System.out.println(getCordName("D G B").toString());
   }

}

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