我正在做一个项目，我需要能够尽可能准确地生成不同频率的 MIDI 音符。我最初尝试用 Java 编写我的程序，但结果表明 sound.midi 包不支持更改音符的调音，除非频率是 Equal Tempered 频率（或者至少在 1.4 中没有，而且我没有t 能够找到证据表明这已在最近的版本中得到修复）。我一直在尝试寻找更合适的语言/库来完成这项任务，但由于这是我第一次使用 MIDI 进行编程，并且我对特定调音功能的需求是必不可少的，因此我很难找到我真正需要的东西。
我正在向有编写 MIDI 程序经验的人寻求关于哪些语言有用的建议，特别是对于将音符调整到特定频率。任何带有 API 文档和示例代码的网站链接也将非常有帮助。
你不能普遍改变调音。这是合成器的一个特性，与 MIDI 无关。
现在，有一些 SysEx 消息通常被理解为这个任务。有关更多信息，请参阅此参考：http: //www.midi.org/techspecs/midituning.php
另一个参考： http: //www.microtonal-synthesis.com/MIDItuning.html
同样，MIDI 只是一个控制协议。产生声音取决于合成器。合成器不必支持更改调音，而且通常不支持。这与 MIDI 无关，也与您发送 MIDI 数据的语言无关。
我的音乐应用程序也遇到了同样的问题。正如@Brad 所假设的，这是一个使用 MIDI 调音标准的解决方案：
步骤是：
Gervills TuningApllet3.java的源代码帮助我完成了这项工作。
Furtunatly，在我使用 Windows 7 和 JDK 1.8 的测试环境中，标准 MIDI 合成器支持 MIDI 调音标准。我不知道是否有可能检查合成器是否支持此标准。
如何计算新频率？
private static float getFrequency(final int keyNumber,
final double concertAFreq) {
// Concert A Pitch is A4 and has the key number 69
final int KEY_A4 = 69;
// Returns the frequency of the given key (equal temperament)
return (float) (concertAFreq * Math.pow(2, (keyNumber - KEY_A4) / 12d));
}
对于毕达哥拉斯调优等其他调优，您可以使用其他计算方法。在这里，我们使用与 MIDI 相同的律动，无需重新调音。
如何将频率转换为频率数据格式？
如频率数据格式中所述，每个频率f必须由 3 个字节表示：
字节 1：基本密钥。在标准 MIDI 调音（等律，A4 = 440 赫兹）中具有低于或等于 f 的频率 f' 的键号
private static int computeBaseKey(final double freq) {
// Concert A Pitch is A4 and has the key number 69
final int A4_KEY = 69;
final double A4_FREQ = 440d;
// Returns the highest key number with a lower or equal frequency than
// freq in standard MIDI frequency mapping (equal temparement, concert
// pitch A4 = 440 Hz).
int baseKey = (int) Math.round((12 * log2(freq / A4_FREQ) + A4_KEY));
double baseFreq = getFrequency(baseKey, A4_FREQ);
if (baseFreq > freq) {
baseKey--;
}
return baseKey;
}
字节 2 和字节 3 ：从f'到f的间隔（以美分为单位）
private static double getCentInterval(final double f1, final double f2) {
// Returns the interval between f1 and f2 in cent
// (100 Cent complies to one semitone)
return 1200d * log2(f2 / f1);
}
这个分区间的整数表示是
tuning = (int) (centInterval * 16384d / 100d);
并且可以使用以下代码拆分为字节 2 和字节 3：
byte2 = (tuning >> 7) & 0x7f; // Higher 7 Bit
byte3 = tuning & 0x7f; // Lower 7 Bit
请注意，并非每个频率都可以用这种格式表示。基本键必须在 0..127 范围内，调整在 0..2^14 - 1 = 0..16383 范围内。另外 (byte1, byte2, byte3) = (0x7f, 0x7f, 0x7f) 被保留。
完整的工作示例
此示例重新调整到 A4 = 500 Hz 并播放从 C4 到 B4 的半音阶：
public static void retune(final Track track, final double concertAFreq) {
if (track == null) {
throw new NullPointerException();
} else if (concertAFreq <= 0) {
throw new IllegalArgumentException("concertAFreq " + concertAFreq
+ " <= 0");
}
final int bank = 0;
final int preset = 0;
final int channel = 0;
addTuningChange(track, channel, preset);
// New frequencies in Hz for the 128 MIDI keys
final double[] frequencies = new double[128];
for (int key = 0; key < 128; key++) {
frequencies[key] = getFrequency(key, concertAFreq);
}
final MidiMessage message = createSingleNoteTuningChange(bank, preset,
frequencies);
track.add(new MidiEvent(message, 0));
}
private static void addTuningChange(final Track track, final int channel,
final int preset) {
try {
// Data Entry
final ShortMessage dataEntry = new ShortMessage(
ShortMessage.CONTROL_CHANGE, channel, 0x64, 03);
final ShortMessage dataEntry2 = new ShortMessage(
ShortMessage.CONTROL_CHANGE, channel, 0x65, 00);
track.add(new MidiEvent(dataEntry, 0));
track.add(new MidiEvent(dataEntry2, 0));
// Tuning program
final ShortMessage tuningProgram = new ShortMessage(
ShortMessage.CONTROL_CHANGE, channel, 0x06, preset);
track.add(new MidiEvent(tuningProgram, 0));
// Data Increment
final ShortMessage dataIncrement = new ShortMessage(
ShortMessage.CONTROL_CHANGE, channel, 0x60, 0x7F);
track.add(new MidiEvent(dataIncrement, 0));
// Data Decrement
final ShortMessage dataDecrement = new ShortMessage(
ShortMessage.CONTROL_CHANGE, channel, 0x61, 0x7F);
track.add(new MidiEvent(dataDecrement, 0));
} catch (final InvalidMidiDataException e) {
throw new AssertionError("Unexpected InvalidMidiDataException", e);
}
}
private static MidiMessage createSingleNoteTuningChange(final int bank,
final int preset, final double[] frequencies) {
// Compute the integer representation of the frequencies
final int[] baseKeys = new int[128];
final int[] tunings = new int[128];
// MIDI Standard tuning frequency
final double STANDARD_A4_FREQ = 440d;
for (int key = 0; key < 128; key++) {
final int baseKey = computeBaseKey(frequencies[key]);
if (baseKey >= 0 && baseKey <= 127) {
final double baseFreq = getFrequency(baseKey, STANDARD_A4_FREQ);
assert baseFreq <= frequencies[key];
final double centInterval = getCentInterval(baseFreq,
frequencies[key]);
baseKeys[key] = baseKey;
tunings[key] = (int) (centInterval * 16384d / 100d);
} else {
// Frequency is out of range. Using default MIDI tuning for it
// TODO: Use LOGGER.warn to warn about
baseKeys[key] = key;
tunings[key] = 0;
}
}
// Data to send
final ByteArrayOutputStream stream = new ByteArrayOutputStream();
stream.write((byte) 0xf0); // SysEx Header
stream.write((byte) 0x7e); // Non-Realtime. For Realtime use 0x7f
stream.write((byte) 0x7f); // Target Device: All Devices
stream.write((byte) 0x08); // MIDI Tuning Standard
stream.write((byte) 0x07); // Single Note Tuning Change Bank
stream.write((byte) bank);
stream.write((byte) preset);
stream.write(128); // Number of keys to retune
for (int key = 0; key < 128; key++) {
stream.write(key); // Key to retune
stream.write(baseKeys[key]);
stream.write((tunings[key] >> 7) & 0x7f); // Higher 7 Bit
stream.write(tunings[key] & 0x7f); // Lower 7 Bit
}
stream.write((byte) 0xf7); // EOX
final byte[] data = stream.toByteArray();
final MidiMessage message;
try {
message = new SysexMessage(data, data.length);
} catch (final InvalidMidiDataException e) {
throw new AssertionError("Unexpected InvalidMidiDataException", e);
}
return message;
}
private static int computeBaseKey(final double freq) {
// Concert A Pitch is A4 and has the key number 69
final int A4_KEY = 69;
final double A4_FREQ = 440d;
// Returns the highest key number with a lower or equal frequency than
// freq in standard MIDI frequency mapping (equal temparement, concert
// pitch A4 = 440 Hz).
int baseKey = (int) Math.round((12 * log2(freq / A4_FREQ) + A4_KEY));
double baseFreq = getFrequency(baseKey, A4_FREQ);
if (baseFreq > freq) {
baseKey--;
}
return baseKey;
}
private static double getCentInterval(final double f1, final double f2) {
// Returns the interval between f1 and f2 in cent
// (100 Cent complies to one semitone)
return 1200d * log2(f2 / f1);
}
private static double log2(final double x) {
// Returns the logarithm dualis (log with base 2)
return Math.log(x) / Math.log(2);
}
private static float getFrequency(final int keyNumber,
final double concertAFreq) {
// Concert A Pitch is A4 and has the key number 69
final int KEY_A4 = 69;
// Returns the frequency of the given key (equal temperament)
return (float) (concertAFreq * Math.pow(2, (keyNumber - KEY_A4) / 12d));
}
public static void main(String[] args) throws Exception {
final int PPQN = 16; // Pulses/Ticks per quarter note
Sequence sequence = new Sequence(Sequence.PPQ, PPQN);
final Track track = sequence.createTrack();
final double a4Freq = 500; // Hz
retune(track, a4Freq);
// Play chromatic Scale from C4 to B4
final int C4_KEY = 60;
final int B4_KEY = 71;
final long quarterTicks = PPQN;
long tick = 0;
for (int key = C4_KEY; key <= B4_KEY; key++) {
final int channel = 0;
final int velocity = 96;
final ShortMessage noteOn = new ShortMessage(ShortMessage.NOTE_ON,
channel, key, velocity);
track.add(new MidiEvent(noteOn, tick));
tick += quarterTicks;
final ShortMessage noteOff = new ShortMessage(
ShortMessage.NOTE_OFF, channel, key, 0);
track.add(new MidiEvent(noteOff, tick));
}
final Sequencer sequencer = MidiSystem.getSequencer();
sequencer.setSequence(sequence);
final CountDownLatch waitForEnd = new CountDownLatch(1);
sequencer.addMetaEventListener(e -> {
if (e.getType() == 47) {
waitForEnd.countDown();
}
});
sequencer.open();
sequencer.start();
System.out.println("started");
waitForEnd.await();
sequencer.stop();
sequencer.close();
System.out.println("ready");
}
我希望使用非实时消息，与实时版本相比，更多的合成器支持这一点。非实时和实时之间的区别应该是，实时允许在播放时重新调整。非实时版本仅影响重新调音后播放的音符。
它有效吗？是的，我已经记录了输出并使用Sonic Visualiser对其进行了分析：
如您所见，频谱图中 A4 的峰值频率接近 500 Hz。