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FA-81676 / MIDI event timing / Open access

Sustain pedal note-off deferral: notes sounding at the end vanish · case 01

Notes still held by the key or pedal when the events end are missing from the output.

Verified by executionVariant 1 · 8 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The final flush of still-sounding notes is missing.

THE FAILURE

The final flush of still-sounding notes is missing.

Unsuccessful approach: Flushing only pedal-held notes still loses notes whose keys were never released.

Case contract

Input time-ordered events [tick, kind, value]: kind on/off with a note number, or cc64 with a controller value (pedal down when value >= 64). A note-off while the pedal is down is deferred until the pedal goes up. Re-striking a note that is still sounding ends the previous instance at the new tick. Notes still sounding at the end end at the last event tick. Return sorted [note, start, end] triples.

Why this case matters

MIDI sequencers, file readers and synth drivers depend on exact event ordering and tick/time arithmetic.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x):
    if not isinstance(x, list):
        return None
    down = False
    sounding = {}
    held = set()
    done = []
    last = 0
    for tick, kind, value in x:
        last = max(last, tick)
        if kind == 'cc64':
            now_down = value >= 64
            if down and not now_down:
                for n in sorted(held):
                    done.append([n, sounding.pop(n), tick])
                held = set()
            down = now_down
        elif kind == 'on':
            if value in sounding:
                done.append([value, sounding.pop(value), tick])
                held.discard(value)
            sounding[value] = tick
        elif kind == 'off':
            if value not in sounding:
                continue
            if down:
                held.add(value)
            else:
                done.append([value, sounding.pop(value), tick])
        else:
            return None
    done.sort()
    return done
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[([[0, 'on', 60], [10, 'off', 60]], [[60, 0, 10]]), ([[0, 'cc64', 127], [0, 'on', 60], [10, 'off', 60], [20, 'cc64', 0]], [[60, 0, 20]]), ([[0, 'cc64', 64], [0, 'on', 60], [10, 'off', 60], [20, 'cc64', 63]], [[60, 0, 20]]), ([[0, 'cc64', 63], [0, 'on', 60], [10, 'off', 60], [20, 'cc64', 0]], [[60, 0, 10]]), ([[0, 'cc64', 100], [0, 'on', 60], [5, 'off', 60], [8, 'on', 60], [12, 'cc64', 0], [30, 'off', 60]], [[60, 0, 8], [60, 8, 30]]), ([[0, 'cc64', 100], [0, 'on', 60], [1, 'on', 64], [5, 'off', 60], [6, 'off', 64], [8, 'on', 60], [12, 'cc64', 0]], [[60, 0, 8], [60, 8, 12], [64, 1, 12]]), ([[0, 'on', 60], [5, 'on', 60], [9, 'off', 60]], [[60, 0, 5], [60, 5, 9]]), ([[0, 'cc64', 127], [0, 'on', 60], [4, 'off', 60], [9, 'on', 62]], [[60, 0, 9], [62, 9, 9]])], [([[0, 'cc64', 63], [0, 'on', 60], [10, 'off', 60], [20, 'cc64', 0]], [[60, 0, 10]]), ([[0, 'cc64', 100], [0, 'on', 60], [5, 'off', 60], [8, 'on', 60], [12, 'cc64', 0], [30, 'off', 60]], [[60, 0, 8], [60, 8, 30]]), ([[0, 'cc64', 100], [0, 'on', 60], [1, 'on', 64], [5, 'off', 60], [6, 'off', 64], [8, 'on', 60], [12, 'cc64', 0]], [[60, 0, 8], [60, 8, 12], [64, 1, 12]]), ([[0, 'on', 60], [5, 'on', 60], [9, 'off', 60]], [[60, 0, 5], [60, 5, 9]]), ([[0, 'on', 60], [0, 'on', 64], [7, 'off', 64]], [[60, 0, 7], [64, 0, 7]]), ([[0, 'cc64', 1], [0, 'on', 60], [3, 'off', 60], [9, 'cc64', 0]], [[60, 0, 3]]), ([[0, 'pb', 0]], None), ([], [])], [([[0, 'cc64', 100], [0, 'on', 60], [1, 'on', 64], [5, 'off', 60], [6, 'off', 64], [8, 'on', 60], [12, 'cc64', 0]], [[60, 0, 8], [60, 8, 12], [64, 1, 12]]), ([[0, 'on', 60], [0, 'on', 64], [7, 'off', 64]], [[60, 0, 7], [64, 0, 7]]), ([[0, 'cc64', 127], [0, 'on', 60], [4, 'off', 60], [9, 'on', 62]], [[60, 0, 9], [62, 9, 9]]), ([[0, 'cc64', 1], [0, 'on', 60], [3, 'off', 60], [9, 'cc64', 0]], [[60, 0, 3]]), ([[0, 'pb', 0]], None), ([], []), ([[0, 'cc64', 127], [1, 'on', 50], [2, 'on', 52], [3, 'off', 50], [4, 'off', 52], [5, 'on', 50], [9, 'off', 50], [12, 'cc64', 0]], [[50, 1, 5], [50, 5, 12], [52, 2, 12]]), ([[0, 'cc64', 127], [1, 'on', 50], [2, 'on', 52], [3, 'off', 50], [4, 'off', 52], [5, 'on', 50], [9, 'off', 50], [12, 'cc64', 0], [15, 'on', 70], [16, 'off', 70]], [[50, 1, 5], [50, 5, 12], [52, 2, 12], [70, 15, 16]])], [([[0, 'on', 60], [10, 'off', 60]], [[60, 0, 10]]), ([[0, 'cc64', 127], [0, 'on', 60], [10, 'off', 60], [20, 'cc64', 0]], [[60, 0, 20]]), ([[0, 'cc64', 64], [0, 'on', 60], [10, 'off', 60], [20, 'cc64', 63]], [[60, 0, 20]]), ([[0, 'cc64', 100], [0, 'on', 60], [1, 'on', 64], [5, 'off', 60], [6, 'off', 64], [8, 'on', 60], [12, 'cc64', 0]], [[60, 0, 8], [60, 8, 12], [64, 1, 12]]), ([[0, 'on', 60], [0, 'on', 64], [7, 'off', 64]], [[60, 0, 7], [64, 0, 7]]), ([[0, 'cc64', 127], [0, 'on', 60], [4, 'off', 60], [9, 'on', 62]], [[60, 0, 9], [62, 9, 9]]), ([[0, 'cc64', 127], [1, 'on', 50], [2, 'on', 52], [3, 'off', 50], [4, 'off', 52], [5, 'on', 50], [9, 'off', 50], [12, 'cc64', 0]], [[50, 1, 5], [50, 5, 12], [52, 2, 12]]), ([[0, 'cc64', 127], [1, 'on', 50], [2, 'on', 52], [3, 'off', 50], [4, 'off', 52], [5, 'on', 50], [9, 'off', 50], [12, 'cc64', 0], [15, 'on', 70], [16, 'off', 70]], [[50, 1, 5], [50, 5, 12], [52, 2, 12], [70, 15, 16]])], [([[0, 'on', 60], [10, 'off', 60]], [[60, 0, 10]]), ([[0, 'cc64', 127], [0, 'on', 60], [10, 'off', 60], [20, 'cc64', 0]], [[60, 0, 20]]), ([[0, 'cc64', 64], [0, 'on', 60], [10, 'off', 60], [20, 'cc64', 63]], [[60, 0, 20]]), ([[0, 'cc64', 63], [0, 'on', 60], [10, 'off', 60], [20, 'cc64', 0]], [[60, 0, 10]]), ([[0, 'cc64', 100], [0, 'on', 60], [5, 'off', 60], [8, 'on', 60], [12, 'cc64', 0], [30, 'off', 60]], [[60, 0, 8], [60, 8, 30]]), ([[0, 'cc64', 100], [0, 'on', 60], [1, 'on', 64], [5, 'off', 60], [6, 'off', 64], [8, 'on', 60], [12, 'cc64', 0]], [[60, 0, 8], [60, 8, 12], [64, 1, 12]]), ([[0, 'on', 60], [0, 'on', 64], [7, 'off', 64]], [[60, 0, 7], [64, 0, 7]]), ([[0, 'cc64', 127], [0, 'on', 60], [4, 'off', 60], [9, 'on', 62]], [[60, 0, 9], [62, 9, 9]])]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("oracle %d" % i, solve(args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
oracle 0[[60, 0, 10]][[60, 0, 10]]Passed
oracle 1[[60, 0, 20]][[60, 0, 20]]Passed
oracle 2[[60, 0, 20]][[60, 0, 20]]Passed
oracle 3[[60, 0, 10]][[60, 0, 10]]Passed
oracle 4[[60, 0, 8], [60, 8, 30]][[60, 0, 8], [60, 8, 30]]Passed
oracle 5[[60, 0, 8], [64, 1, 12]][[60, 0, 8], [60, 8, 12], [64, 1, 12]]Failed
oracle 6[[60, 0, 5], [60, 5, 9]][[60, 0, 5], [60, 5, 9]]Passed
oracle 7[][[60, 0, 9], [62, 9, 9]]Failed

SHA-256 / ef5f23fe6d764d0b7589c0becb1d38ff197ea88289c2cf21ac08f2e298ee5bd4

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x):
    if not isinstance(x, list):
        return None
    down = False
    sounding = {}
    held = set()
    done = []
    last = 0
    for tick, kind, value in x:
        last = max(last, tick)
        if kind == 'cc64':
            now_down = value >= 64
            if down and not now_down:
                for n in sorted(held):
                    done.append([n, sounding.pop(n), tick])
                held = set()
            down = now_down
        elif kind == 'on':
            if value in sounding:
                done.append([value, sounding.pop(value), tick])
                held.discard(value)
            sounding[value] = tick
        elif kind == 'off':
            if value not in sounding:
                continue
            if down:
                held.add(value)
            else:
                done.append([value, sounding.pop(value), tick])
        else:
            return None
    for n in sorted(held):
        done.append([n, sounding[n], last])
    done.sort()
    return done
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[([[0, 'on', 60], [10, 'off', 60]], [[60, 0, 10]]), ([[0, 'cc64', 127], [0, 'on', 60], [10, 'off', 60], [20, 'cc64', 0]], [[60, 0, 20]]), ([[0, 'cc64', 64], [0, 'on', 60], [10, 'off', 60], [20, 'cc64', 63]], [[60, 0, 20]]), ([[0, 'cc64', 63], [0, 'on', 60], [10, 'off', 60], [20, 'cc64', 0]], [[60, 0, 10]]), ([[0, 'cc64', 100], [0, 'on', 60], [5, 'off', 60], [8, 'on', 60], [12, 'cc64', 0], [30, 'off', 60]], [[60, 0, 8], [60, 8, 30]]), ([[0, 'cc64', 100], [0, 'on', 60], [1, 'on', 64], [5, 'off', 60], [6, 'off', 64], [8, 'on', 60], [12, 'cc64', 0]], [[60, 0, 8], [60, 8, 12], [64, 1, 12]]), ([[0, 'on', 60], [5, 'on', 60], [9, 'off', 60]], [[60, 0, 5], [60, 5, 9]]), ([[0, 'cc64', 127], [0, 'on', 60], [4, 'off', 60], [9, 'on', 62]], [[60, 0, 9], [62, 9, 9]])], [([[0, 'cc64', 63], [0, 'on', 60], [10, 'off', 60], [20, 'cc64', 0]], [[60, 0, 10]]), ([[0, 'cc64', 100], [0, 'on', 60], [5, 'off', 60], [8, 'on', 60], [12, 'cc64', 0], [30, 'off', 60]], [[60, 0, 8], [60, 8, 30]]), ([[0, 'cc64', 100], [0, 'on', 60], [1, 'on', 64], [5, 'off', 60], [6, 'off', 64], [8, 'on', 60], [12, 'cc64', 0]], [[60, 0, 8], [60, 8, 12], [64, 1, 12]]), ([[0, 'on', 60], [5, 'on', 60], [9, 'off', 60]], [[60, 0, 5], [60, 5, 9]]), ([[0, 'on', 60], [0, 'on', 64], [7, 'off', 64]], [[60, 0, 7], [64, 0, 7]]), ([[0, 'cc64', 1], [0, 'on', 60], [3, 'off', 60], [9, 'cc64', 0]], [[60, 0, 3]]), ([[0, 'pb', 0]], None), ([], [])], [([[0, 'cc64', 100], [0, 'on', 60], [1, 'on', 64], [5, 'off', 60], [6, 'off', 64], [8, 'on', 60], [12, 'cc64', 0]], [[60, 0, 8], [60, 8, 12], [64, 1, 12]]), ([[0, 'on', 60], [0, 'on', 64], [7, 'off', 64]], [[60, 0, 7], [64, 0, 7]]), ([[0, 'cc64', 127], [0, 'on', 60], [4, 'off', 60], [9, 'on', 62]], [[60, 0, 9], [62, 9, 9]]), ([[0, 'cc64', 1], [0, 'on', 60], [3, 'off', 60], [9, 'cc64', 0]], [[60, 0, 3]]), ([[0, 'pb', 0]], None), ([], []), ([[0, 'cc64', 127], [1, 'on', 50], [2, 'on', 52], [3, 'off', 50], [4, 'off', 52], [5, 'on', 50], [9, 'off', 50], [12, 'cc64', 0]], [[50, 1, 5], [50, 5, 12], [52, 2, 12]]), ([[0, 'cc64', 127], [1, 'on', 50], [2, 'on', 52], [3, 'off', 50], [4, 'off', 52], [5, 'on', 50], [9, 'off', 50], [12, 'cc64', 0], [15, 'on', 70], [16, 'off', 70]], [[50, 1, 5], [50, 5, 12], [52, 2, 12], [70, 15, 16]])], [([[0, 'on', 60], [10, 'off', 60]], [[60, 0, 10]]), ([[0, 'cc64', 127], [0, 'on', 60], [10, 'off', 60], [20, 'cc64', 0]], [[60, 0, 20]]), ([[0, 'cc64', 64], [0, 'on', 60], [10, 'off', 60], [20, 'cc64', 63]], [[60, 0, 20]]), ([[0, 'cc64', 100], [0, 'on', 60], [1, 'on', 64], [5, 'off', 60], [6, 'off', 64], [8, 'on', 60], [12, 'cc64', 0]], [[60, 0, 8], [60, 8, 12], [64, 1, 12]]), ([[0, 'on', 60], [0, 'on', 64], [7, 'off', 64]], [[60, 0, 7], [64, 0, 7]]), ([[0, 'cc64', 127], [0, 'on', 60], [4, 'off', 60], [9, 'on', 62]], [[60, 0, 9], [62, 9, 9]]), ([[0, 'cc64', 127], [1, 'on', 50], [2, 'on', 52], [3, 'off', 50], [4, 'off', 52], [5, 'on', 50], [9, 'off', 50], [12, 'cc64', 0]], [[50, 1, 5], [50, 5, 12], [52, 2, 12]]), ([[0, 'cc64', 127], [1, 'on', 50], [2, 'on', 52], [3, 'off', 50], [4, 'off', 52], [5, 'on', 50], [9, 'off', 50], [12, 'cc64', 0], [15, 'on', 70], [16, 'off', 70]], [[50, 1, 5], [50, 5, 12], [52, 2, 12], [70, 15, 16]])], [([[0, 'on', 60], [10, 'off', 60]], [[60, 0, 10]]), ([[0, 'cc64', 127], [0, 'on', 60], [10, 'off', 60], [20, 'cc64', 0]], [[60, 0, 20]]), ([[0, 'cc64', 64], [0, 'on', 60], [10, 'off', 60], [20, 'cc64', 63]], [[60, 0, 20]]), ([[0, 'cc64', 63], [0, 'on', 60], [10, 'off', 60], [20, 'cc64', 0]], [[60, 0, 10]]), ([[0, 'cc64', 100], [0, 'on', 60], [5, 'off', 60], [8, 'on', 60], [12, 'cc64', 0], [30, 'off', 60]], [[60, 0, 8], [60, 8, 30]]), ([[0, 'cc64', 100], [0, 'on', 60], [1, 'on', 64], [5, 'off', 60], [6, 'off', 64], [8, 'on', 60], [12, 'cc64', 0]], [[60, 0, 8], [60, 8, 12], [64, 1, 12]]), ([[0, 'on', 60], [0, 'on', 64], [7, 'off', 64]], [[60, 0, 7], [64, 0, 7]]), ([[0, 'cc64', 127], [0, 'on', 60], [4, 'off', 60], [9, 'on', 62]], [[60, 0, 9], [62, 9, 9]])]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("oracle %d" % i, solve(args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
oracle 0[[60, 0, 10]][[60, 0, 10]]Passed
oracle 1[[60, 0, 20]][[60, 0, 20]]Passed
oracle 2[[60, 0, 20]][[60, 0, 20]]Passed
oracle 3[[60, 0, 10]][[60, 0, 10]]Passed
oracle 4[[60, 0, 8], [60, 8, 30]][[60, 0, 8], [60, 8, 30]]Passed
oracle 5[[60, 0, 8], [64, 1, 12]][[60, 0, 8], [60, 8, 12], [64, 1, 12]]Failed
oracle 6[[60, 0, 5], [60, 5, 9]][[60, 0, 5], [60, 5, 9]]Passed
oracle 7[[60, 0, 9]][[60, 0, 9], [62, 9, 9]]Failed

SHA-256 / 4287ed64e028c8c4f5fd7487e70810c42897b8b316cc01d863c72798bee4d22f

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 8 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

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Verification & scope

A deterministic bounded teaching model with a stipulated toy contract; it is not a complete Standard MIDI File or MIDI 1.0/2.0 implementation. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:50:05.120082+00:00.

Case digest / b14f4971e5fa9475d457ef3a204dd3b40dfb940070c73f15b4fa4c94d9ca8cf1