1CHORD_ERROR_MESSAGE = "Cannot have a chord made of only 1 unique tone"
  2INVALID_OPERATION_MESSAGE = "Invalid operation"
  3TONES = ["C", "C#", "D", "D#", "E", "F", "F#", "G", "G#", "A", "A#", "B"]
  4INTERVALS = ["unison", "minor 2nd", "major 2nd", "minor 3rd", "major 3rd", "perfect 4th", "diminished 5th", "perfect 5th", "minor 6th", "major 6th", "minor 7th", "major 7th"]
  5
  6class Tone:
  7    def __init__(self, tone):
  8        self.tone = tone
  9
 10    def __str__(self):
 11        return str(self.tone)
 12    
 13    def __iter__(self):
 14        return iter(self.tone)
 15
 16    def __add__(self, other):
 17        if isinstance(other, Tone):
 18            return Chord(self, other)
 19        if isinstance(other, Interval): 
 20            return Tone(TONES[(TONES.index(str(self)) + other.num_of_semitones) % len(TONES)])
 21
 22    def __sub__(self, other):
 23        if isinstance(other, Tone):
 24            return Interval(abs(TONES.index(str(self)) - TONES.index(str(other))))
 25        if isinstance(other, Interval): 
 26            return Tone(TONES[(TONES.index(str(self)) - other.num_of_semitones) % len(TONES)])
 27        
 28
 29class Interval:
 30    def __init__(self, num_of_tones):
 31        self.is_positive = num_of_tones >= 0
 32        num_of_tones = abs(num_of_tones)
 33        self.num_of_semitones = num_of_tones % len(INTERVALS)
 34    
 35    def __str__(self):
 36        return str(INTERVALS[self.num_of_semitones])
 37    
 38    def __int__(self):
 39        return self.num_of_semitones
 40    
 41    def __add__(self, other):
 42        if isinstance(other, Tone):
 43            raise TypeError(INVALID_OPERATION_MESSAGE)
 44        if isinstance(other, Interval):
 45            return Interval(int(self) + int(other))
 46
 47    def __sub__(self, other):
 48        if isinstance(other, Tone):
 49            raise TypeError(INVALID_OPERATION_MESSAGE)
 50        
 51    def __neg__(self):
 52        return Interval(-self.num_of_semitones)
 53
 54class Chord:
 55    def __init__(self, *tones):
 56        self.tones = []
 57        for tone in tones:
 58            if str(tone) not in self.tones:
 59                self.tones.append(str(tone))
 60        self.root = self.tones[0]
 61        if len(self.tones) == 1:
 62            raise TypeError(CHORD_ERROR_MESSAGE)
 63        tone_index = TONES.index(str(self.root))
 64        self.scale = TONES[tone_index:] + TONES[:tone_index]
 65        self.tones = sorted(self.tones, key=lambda tone: self.scale.index(str(tone))) 
 66        
 67    def __str__(self):
 68        return '-'.join(map(str, self.tones))
 69
 70    def is_major(self):
 71        for tone in self.tones:
 72            if abs(TONES.index(str(self.root)) - TONES.index(str(tone))) == INTERVALS.index("major 3rd"):
 73                return True
 74        return False
 75    
 76    def is_minor(self):
 77        for tone in self.tones:
 78            if abs(TONES.index(str(self.root)) - TONES.index(str(tone))) == INTERVALS.index("minor 3rd"):
 79                return True
 80        return False
 81    
 82    def is_power_chord(self):
 83        if self.is_minor() or self.is_major():
 84            return False
 85        return True
 86    
 87    def __add__(self, other):
 88        if isinstance(other, Tone):
 89            new_tones = self.tones + [other]
 90        if isinstance(other, Chord):
 91            new_tones = self.tones + other.tones
 92        return Chord(*new_tones)
 93
 94    def __sub__(self, other):
 95        if isinstance(other, Tone):
 96            if str(other) not in self.tones:
 97                raise TypeError(f"Cannot remove tone {other} from chord {str(self)}")
 98            if len(self.tones) < 3:
 99                raise TypeError("Cannot have a chord made of only 1 unique tone")
100            to_return = Chord(*self.tones)
101            if str(other) == str(to_return.root):
102                to_return.root = to_return.tones[1]
103                del to_return.tones[0]
104            else:
105                other_index = to_return.tones.index(str(other))
106                del to_return.tones[other_index]
107            return to_return
108
109    def transposed(self, interval):
110        if isinstance(interval, Interval):
111            new_tones = []
112            direction = 1 if interval.is_positive else -1
113            for tone in self.tones:
114                new_index = self.scale.index(str(tone)) + direction*int(interval)
115                new_tones.append(str(self.scale[new_index]))
116            return Chord(*new_tones)