diff --git a/src/main/resources/db/migration/V3__normalize_legacy_playing_midi_data.sql b/src/main/resources/db/migration/V3__normalize_legacy_playing_midi_data.sql
new file mode 100644
index 00000000..b8232c29
--- /dev/null
+++ b/src/main/resources/db/migration/V3__normalize_legacy_playing_midi_data.sql
@@ -0,0 +1,116 @@
+DO
+$$
+DECLARE
+    playing_row RECORD;
+    midi_event JSONB;
+    event_ordinality BIGINT;
+    timestamp_value JSONB;
+    numeric_value NUMERIC;
+BEGIN
+    FOR playing_row IN
+        SELECT playing_id, midi_data
+        FROM playing
+        WHERE midi_data IS NOT NULL
+    LOOP
+        IF jsonb_typeof(playing_row.midi_data) IS DISTINCT FROM 'array' THEN
+            RAISE EXCEPTION 'playing %.midi_data must be a JSON array', playing_row.playing_id;
+        END IF;
+
+        FOR midi_event, event_ordinality IN
+            SELECT value, ordinality
+            FROM jsonb_array_elements(playing_row.midi_data) WITH ORDINALITY
+        LOOP
+            IF jsonb_typeof(midi_event) IS DISTINCT FROM 'object' THEN
+                RAISE EXCEPTION 'playing %.midi_data[%] must be a JSON object',
+                    playing_row.playing_id, event_ordinality - 1;
+            END IF;
+
+            IF jsonb_typeof(midi_event -> 'type') IS DISTINCT FROM 'string'
+                OR midi_event ->> 'type' NOT IN ('NOTE_ON', 'NOTE_OFF') THEN
+                RAISE EXCEPTION 'playing %.midi_data[%] has an invalid type',
+                    playing_row.playing_id, event_ordinality - 1;
+            END IF;
+
+            IF jsonb_typeof(midi_event -> 'pitch') IS DISTINCT FROM 'number' THEN
+                RAISE EXCEPTION 'playing %.midi_data[%] has an invalid pitch',
+                    playing_row.playing_id, event_ordinality - 1;
+            END IF;
+            numeric_value := (midi_event ->> 'pitch')::NUMERIC;
+            IF numeric_value <> trunc(numeric_value) OR numeric_value < 0 OR numeric_value > 127 THEN
+                RAISE EXCEPTION 'playing %.midi_data[%] has an invalid pitch',
+                    playing_row.playing_id, event_ordinality - 1;
+            END IF;
+
+            IF jsonb_typeof(midi_event -> 'velocity') IS DISTINCT FROM 'number' THEN
+                RAISE EXCEPTION 'playing %.midi_data[%] has an invalid velocity',
+                    playing_row.playing_id, event_ordinality - 1;
+            END IF;
+            numeric_value := (midi_event ->> 'velocity')::NUMERIC;
+            IF numeric_value <> trunc(numeric_value) OR numeric_value < 0 OR numeric_value > 127 THEN
+                RAISE EXCEPTION 'playing %.midi_data[%] has an invalid velocity',
+                    playing_row.playing_id, event_ordinality - 1;
+            END IF;
+
+            timestamp_value := COALESCE(
+                NULLIF(midi_event -> 'timestamp_ms', 'null'::JSONB),
+                NULLIF(midi_event -> 'timestampMs', 'null'::JSONB)
+            );
+            IF jsonb_typeof(timestamp_value) IS DISTINCT FROM 'number' THEN
+                RAISE EXCEPTION 'playing %.midi_data[%] has an invalid timestamp',
+                    playing_row.playing_id, event_ordinality - 1;
+            END IF;
+            numeric_value := (timestamp_value #>> '{}')::NUMERIC;
+            IF numeric_value <> trunc(numeric_value) OR numeric_value < 0 OR numeric_value > 9223372036854775807 THEN
+                RAISE EXCEPTION 'playing %.midi_data[%] has an invalid timestamp',
+                    playing_row.playing_id, event_ordinality - 1;
+            END IF;
+
+            IF NULLIF(midi_event -> 'sequence', 'null'::JSONB) IS NOT NULL THEN
+                IF jsonb_typeof(midi_event -> 'sequence') IS DISTINCT FROM 'number' THEN
+                    RAISE EXCEPTION 'playing %.midi_data[%] has an invalid sequence',
+                        playing_row.playing_id, event_ordinality - 1;
+                END IF;
+                numeric_value := (midi_event ->> 'sequence')::NUMERIC;
+                IF numeric_value <> trunc(numeric_value) OR numeric_value < 0 OR numeric_value > 2147483647 THEN
+                    RAISE EXCEPTION 'playing %.midi_data[%] has an invalid sequence',
+                        playing_row.playing_id, event_ordinality - 1;
+                END IF;
+            END IF;
+        END LOOP;
+    END LOOP;
+END
+$$;
+
+UPDATE playing AS p
+SET midi_data = CASE
+    WHEN p.midi_data IS NULL THEN '[]'::JSONB
+    ELSE COALESCE(
+        (
+            SELECT jsonb_agg(
+                (midi_event - 'timestampMs' - 'sequence')
+                    || jsonb_build_object(
+                        'sequence', COALESCE(
+                            NULLIF(midi_event -> 'sequence', 'null'::JSONB),
+                            to_jsonb((event_ordinality - 1)::INTEGER)
+                        ),
+                        'timestamp_ms', COALESCE(
+                            NULLIF(midi_event -> 'timestamp_ms', 'null'::JSONB),
+                            NULLIF(midi_event -> 'timestampMs', 'null'::JSONB)
+                        )
+                    )
+                ORDER BY event_ordinality
+            )
+            FROM jsonb_array_elements(p.midi_data) WITH ORDINALITY
+                AS events(midi_event, event_ordinality)
+        ),
+        '[]'::JSONB
+    )
+END
+WHERE p.midi_data IS NULL
+   OR EXISTS (
+        SELECT 1
+        FROM jsonb_array_elements(p.midi_data) AS events(midi_event)
+        WHERE NULLIF(midi_event -> 'sequence', 'null'::JSONB) IS NULL
+           OR NULLIF(midi_event -> 'timestamp_ms', 'null'::JSONB) IS NULL
+           OR midi_event ? 'timestampMs'
+    );