Below are five buttons.

One plays the DSU and the other four raise and lower each string.

Move the DSU less than 0.5 cents:

1) Detune one string of the DSU the smallest amount possible.

2) Then tune the other string so that the DSU is clean again.

You must move the DSU less than 0.5 cents, and you must retune the DSU to be a clean unison again.

Notes:
To simulate the effect of friction, sometimes the pitch won't change when you click Raise or Lower.
Also, sometimes the pitch will jump more than other times. This gives the feel of tuning a real piano.
Sometimes the strings won't sound together. Just click Play DSU and that should fix it.
If you are having trouble, try a different browser or device.

Play DSU

String #1

Raise String #1 Lower String #1

String #2

Raise String #2 Lower String #2

Results will be posted here.

[tcb-script] (function () { const sounds = [ "https://howtotunepianos.com/wp-content/uploads/2018/08/A3-1b.mp3", "https://howtotunepianos.com/wp-content/uploads/2018/08/A3-2b.mp3", "https://howtotunepianos.com/wp-content/uploads/2018/08/A3-3b.mp3", "https://howtotunepianos.com/wp-content/uploads/2018/08/A3-4b.mp3", "https://howtotunepianos.com/wp-content/uploads/2018/08/A3-5b.mp3", "https://howtotunepianos.com/wp-content/uploads/2018/08/A3-6b.mp3", "https://howtotunepianos.com/wp-content/uploads/2018/08/A3-7b.mp3", "https://howtotunepianos.com/wp-content/uploads/2018/08/A3-8b.mp3", "https://howtotunepianos.com/wp-content/uploads/2018/08/A3-9b.mp3", "https://howtotunepianos.com/wp-content/uploads/2018/08/A3-10b.mp3", "https://howtotunepianos.com/wp-content/uploads/2018/08/A3-11b.mp3", "https://howtotunepianos.com/wp-content/uploads/2018/08/A3-12b.mp3", "https://howtotunepianos.com/wp-content/uploads/2018/08/A3-13b.mp3", "https://howtotunepianos.com/wp-content/uploads/2018/08/A3-14b.mp3", "https://howtotunepianos.com/wp-content/uploads/2018/08/A3-15b.mp3", "https://howtotunepianos.com/wp-content/uploads/2018/08/A3-16b.mp3", "https://howtotunepianos.com/wp-content/uploads/2018/08/A3-17b.mp3" ]; const pitches = [-1.4, -1.2, -1.1, -0.9, -0.7, -0.6, -0.4, -0.2, 0.0, 0.1, 0.3, 0.5, 0.6, 0.8, 1.0, 1.2, 1.3]; let string1 = 8; let string2 = 8; let currentSources = []; let playRequestNumber = 0; const AudioContextClass = window.AudioContext || window.webkitAudioContext; const audioContext = new AudioContextClass(); const bufferPromises = new Map(); const startOffsets = new Map(); const string1Result = document.getElementById("dsu-string-1"); const string2Result = document.getElementById("dsu-string-2"); const differenceResult = document.getElementById("dsu-difference"); const answerResult = document.getElementById("dsu-answer"); function formatPitch(value) { return value.toFixed(1); } function getDifference() { return Math.round(Math.abs(pitches[string1] - pitches[string2]) * 10) / 10; } function loadBuffer(url) { if (!bufferPromises.has(url)) { const bufferPromise = fetch(url) .then(function (response) { if (!response.ok) { throw new Error("Audio file could not be loaded."); } return response.arrayBuffer(); }) .then(function (arrayBuffer) { return audioContext.decodeAudioData(arrayBuffer); }); bufferPromises.set(url, bufferPromise); } return bufferPromises.get(url); } function findStartOffset(buffer) { if (startOffsets.has(buffer)) { return startOffsets.get(buffer); } let maximum = 0; for (let channel = 0; channel < buffer.numberOfChannels; channel += 1) { const samples = buffer.getChannelData(channel); for (let i = 0; i < samples.length; i += 1) { maximum = Math.max(maximum, Math.abs(samples[i])); } } const threshold = maximum * 0.02; let firstSoundSample = buffer.length; for (let channel = 0; channel < buffer.numberOfChannels; channel += 1) { const samples = buffer.getChannelData(channel); for (let i = 0; i < samples.length; i += 1) { if (Math.abs(samples[i]) >= threshold) { firstSoundSample = Math.min(firstSoundSample, i); break; } } } const fiveMilliseconds = Math.round(buffer.sampleRate * 0.005); const offset = Math.max(0, firstSoundSample - fiveMilliseconds) / buffer.sampleRate; startOffsets.set(buffer, offset); return offset; } function stopCurrentSources() { currentSources.forEach(function (source) { try { source.stop(); } catch (error) { /* The source may already have stopped. */ } }); currentSources = []; } async function playDSU() { const thisRequest = ++playRequestNumber; stopCurrentSources(); string1Result.textContent = "Pitch of string #1: " + formatPitch(pitches[string1]) + " cents"; string2Result.textContent = "Pitch of string #2: " + formatPitch(pitches[string2]) + " cents"; differenceResult.textContent = "Difference: " + formatPitch(getDifference()) + " cents"; if (!bufferPromises.has(sounds[string1]) || !bufferPromises.has(sounds[string2])) { answerResult.textContent = "Loading audio…"; } try { const buffers = await Promise.all([ loadBuffer(sounds[string1]), loadBuffer(sounds[string2]) ]); if (thisRequest !== playRequestNumber) { return; } await audioContext.resume(); const source1 = audioContext.createBufferSource(); const source2 = audioContext.createBufferSource(); source1.buffer = buffers[0]; source2.buffer = buffers[1]; source1.connect(audioContext.destination); source2.connect(audioContext.destination); currentSources = [source1, source2]; const startTime = audioContext.currentTime + 0.04; source1.start(startTime, findStartOffset(buffers[0])); source2.start(startTime, findStartOffset(buffers[1])); if (answerResult.textContent === "Loading audio…") { answerResult.textContent = ""; } } catch (error) { if (thisRequest === playRequestNumber) { answerResult.textContent = "The audio could not be played. Click Play DSU to try again."; } } } function checkResult() { const difference = getDifference(); if (difference !== 0) { answerResult.textContent = "The unison is not clean."; return; } const amountMoved = Math.abs(pitches[string1]); if (amountMoved === 0) { answerResult.textContent = "Pitch hasn't changed.nGo to the next lesson now and try it again without the numbers."; } else if (amountMoved < 0.5) { answerResult.textContent = "Excellent! You have moved the pitch only " + formatPitch(amountMoved) + " cents and retuned it as a clean unison.nGo to the next lesson now and try it again without the numbers."; } else { answerResult.textContent = "Your unison is clean, but you have moved the pitch " + formatPitch(amountMoved) + " cents. That's too much.nGo to the next lesson now and try it again without the numbers."; } } function moveString(stringNumber, direction) { const frictionAllowsMovement = Math.random() > 0.4; if (frictionAllowsMovement) { const jump = Math.floor(Math.random() * 3) + 1; if (stringNumber === 1) { const nextPosition = string1 + direction * jump; if (nextPosition > sounds.length - 1) { string1 = sounds.length - 1; alert("String #1 can't go any higher."); } else if (nextPosition < 0) { string1 = 0; alert("String #1 can't go any lower."); } else { string1 = nextPosition; } } else { const nextPosition = string2 + direction * jump; if (nextPosition > sounds.length - 1) { string2 = sounds.length - 1; alert("String #2 can't go any higher."); } else if (nextPosition < 0) { string2 = 0; alert("String #2 can't go any lower."); } else { string2 = nextPosition; } } } playDSU(); checkResult(); } document.getElementById("dsu-play").addEventListener("click", playDSU); document.getElementById("dsu-raise-1").addEventListener("click", function () { moveString(1, 1); }); document.getElementById("dsu-raise-2").addEventListener("click", function () { moveString(2, 1); }); document.getElementById("dsu-lower-1").addEventListener("click", function () { moveString(1, -1); }); document.getElementById("dsu-lower-2").addEventListener("click", function () { moveString(2, -1); }); sounds.forEach(function (url) { loadBuffer(url).catch(function () { /* A failed file will be reported if the user tries to play it. */ }); }); })(); [/tcb-script]

Exercise – DSU Practice – Level 1

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