matlab实现电子钢琴程序，给出基准节拍，并定义每个音乐频率，导入文本文件，可输出一段音乐

A：

首先，我们需要定义基准节拍和每个音乐频率：

% 基准节拍(秒)
beat = 0.25;

% 每个音乐频率
freqs = [
    261.63, % 中音C
    293.66, % 中音D
    329.63, % 中音E
    349.23, % 中音F
    392.00, % 中音G
    440.00, % 中音A
    493.88  % 中音B
];

然后，我们可以从文本文件中读取音符和时长，并根据这些信息构建音乐：

% 从文本文件读取音符和时长
filename = 'music.txt';
fileID = fopen(filename);
data = textscan(fileID, '%s %f');
fclose(fileID);

% 构建音乐
music = [];
for i = 1:length(data{1})
    note = data{1}{i};
    duration = data{2}(i);
    freq_index = str2double(note(2:end));
    freq = freqs(freq_index);
    switch note(1)
        case 'C'
            note_data = sin(2 * pi * freq * (0:1/fs:duration-beat));
        case 'D'
            note_data = sin(2 * pi * freq * (0:1/fs:duration-beat));
        case 'E'
            note_data = sin(2 * pi * freq * (0:1/fs:duration-beat));
        case 'F'
            note_data = sin(2 * pi * freq * (0:1/fs:duration-beat));
        case 'G'
            note_data = sin(2 * pi * freq * (0:1/fs:duration-beat));
        case 'A'
            note_data = sin(2 * pi * freq * (0:1/fs:duration-beat));
        case 'B'
            note_data = sin(2 * pi * freq * (0:1/fs:duration-beat));
    end
    music = [music, note_data];
end

最后，我们可以输出音乐：

% 输出音乐
sound(music, fs);

完整代码如下：

% 基准节拍(秒)
beat = 0.25;

% 每个音乐频率
freqs = [
    261.63, % 中音C
    293.66, % 中音D
    329.63, % 中音E
    349.23, % 中音F
    392.00, % 中音G
    440.00, % 中音A
    493.88  % 中音B
];

% 从文本文件读取音符和时长
filename = 'music.txt';
fileID = fopen(filename);
data = textscan(fileID, '%s %f');
fclose(fileID);

% 构建音乐
music = [];
for i = 1:length(data{1})
    note = data{1}{i};
    duration = data{2}(i);
    freq_index = str2double(note(2:end));
    freq = freqs(freq_index);
    switch note(1)
        case 'C'
            note_data = sin(2 * pi * freq * (0:1/fs:duration-beat));
        case 'D'
            note_data = sin(2 * pi * freq * (0:1/fs:duration-beat));
        case 'E'
            note_data = sin(2 * pi * freq * (0:1/fs:duration-beat));
        case 'F'
            note_data = sin(2 * pi * freq * (0:1/fs:duration-beat));
        case 'G'
            note_data = sin(2 * pi * freq * (0:1/fs:duration-beat));
        case 'A'
            note_data = sin(2 * pi * freq * (0:1/fs:duration-beat));
        case 'B'
            note_data = sin(2 * pi * freq * (0:1/fs:duration-beat));
    end
    music = [music, note_data];
end

% 输出音乐
sound(music, fs);