Goal The purpose of this project is to write a program to generate a two-part waltz by pasting together 32 of 272 precomposed musical elements at random, and another program to play the waltz.

In 1787, Wolfgang Amadeus Mozart created a dice game (Mozart’s Musikalisches W¨urfelspiel). In the game, you compose a two part waltz by pasting together 32 of 272 pre-composed musical elements at random

The Waltz The waltz consists of two parts — the minuet and the trio. Each is comprised of 16 measures, which are generated at random according to a fixed set of rules, as described below.

• Minuet The minuet consists of 16 measures. There are 176 possible minuet measures, named M1.wav through M176.wav in the data directory. To determine which one to play, roll two fair dice, and use the following table:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

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2 96 22 141 41 105 122 11 30 70 121 26 9 112 49 109 14

3 32 6 128 63 146 46 134 81 117 39 126 56 174 18 116 83

4 69 95 158 13 153 55 110 24 66 139 15 132 73 58 145 79

5 40 17 113 85 161 2 159 100 90 176 7 34 67 160 52 170

6 148 74 163 45 80 97 36 107 25 143 64 125 76 136 1 93

7 104 157 27 167 154 68 118 91 138 71 150 29 101 162 23 151

8 152 60 171 53 99 133 21 127 16 155 57 175 43 168 89 172

9 119 84 114 50 140 86 169 94 120 88 48 166 51 115 72 111

10 98 142 42 156 75 129 62 123 65 77 19 82 137 38 149 8

11 3 87 165 61 135 47 147 33 102 4 31 164 144 59 173 78

12 54 130 10 103 28 37 106 5 35 20 108 92 12 124 44 131

For example, if you roll a 4 and 6 for measure 8, then play measure 123 (ie, data/M123.wav).

• Trio The trio also consists of 16 measures. There are 96 possible trio measures named T1.wav through T96.wav in the data directory. To determine which one to play, roll one fair die, and use the following table:

17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

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1 72 6 59 25 81 41 89 13 36 5 46 79 30 95 19 66

2 56 82 42 74 14 7 26 71 76 20 64 84 8 35 47 88

3 75 39 54 1 65 43 15 80 9 34 93 48 69 58 90 21

4 40 73 16 68 29 55 2 61 22 67 49 77 57 87 33 10

5 83 3 28 53 37 17 44 70 63 85 32 96 12 23 50 91

6 18 45 62 38 4 27 52 94 11 92 24 86 51 60 78 31

For example, if you roll a 4 for measure 29, then play measure 57 (ie, data/T57.wav).

Data The 272 measures are available as .wav files in the data directory. The file data/mozart.txt contains the values of the minuet and trio tables.

Composition The file data/mozart.wav is a sample waltz generated using the process described above. There are 1116 × 6 16 different possible results, some of which are more likely than others. Since this is over 1023 different possibilities, each time you play the game you are likely to compose a piece of music that has never been heard before! Mozart carefully constructed the measures to obey a rigid harmonic structure, so each waltz reflects Mozart’s distinct style. Unfortunately, due to the rigidity, the process never results in anything truly extraordinary.

Problem 1. (Generating the Waltz ) Write a program called generatewaltz.py that accepts the minuet and trio tables from standard input, generates a random sequence of 32 measures according to the rules described above, and writes the sequence to standard output.

Hints: • Read the minuet measures from standard input into a 2D list with dimensions 11 × 16 • Read the trio measures from standard input into a 2D list with dimensions 6 × 16 • Write to standard output a random sequence of 16 minuet measures, each of which is a value from the minuet table — the column index j is a value from [0, 15] and the row index i ∈ [0, 10] is obtained from the sum of two die rolls • Write to standard output a random sequence of 16 trio measures, each of which is a value from the trio table — the column index j is a value from [0, 15] and the row index i ∈ [0, 5] is obtained from a die roll

& ~/workspace/project3 $ python3 generatewaltz . py < data / mozart . txt

69 95 27 103 105 129 21 24 66 155 48 34 43 18 89 78 72 39 59 68 29 7 15 94 76 34 93 77 12 95 47 10

Problem 2. (Playing the Waltz ) Write a program called playwaltz.py that accepts from standard input, a sequence of 32 integers representing the 32 measures of a waltz, and plays the waltz to standard audio. Before playing any audio, your program must check if the inputs are correct, and if they are not, must call sys.exit(message) to exit the program with an appropriate error message. The following errors must be handled:

• If the number of measures is not 32, exit with the message “A waltz must contain exactly 32 measures”.

• If a minuet measure is not from [1, 176], exit with the message “A minuet measure must be from [1, 176]”.

• If a trio measure is not from [1, 96], exit with the message “A trio measure must be from [1, 96]”.

Hints: • Read the waltz measures from standard input into a 1D list • Handle the input errors described in the project writeup • Play each of the first 16 minuet measures by calling stdaudio.playFile(f), where f is the filename of the minuet (eg, if the measure is 123, then f = ’data/M123’) • Play each of the last 16 trio measures by calling stdaudio.playFile(f), where f is the filename of the trio (eg, if the measure is 57, then f = ’data/T57’)

The data directory contains: • The 272 measures as .wav files • The values of the minuet and trio tables in mozart.txt • A sample waltz mozart.wav generated using the process described in the project writeup