Sitting alone and looking back, the speaker drifts into memories of childhood, especially Christmas. They remember a feeling of joy, the sight of trains moving, and laughing so hard with their dad that it felt like crying out. Music from those days seems to hum right through their bones, and they sing along even without knowing the words, which makes the scene feel innocent and carefree.
The tape imagery matters. The speaker plays the past like a recording, and the phrase "bittersweet montage" tells us these memories bring both warmth and ache. The opening line, wondering if they "also shared the days," suggests a slight distance, as if that younger self is almost a stranger. The word "vermilon," a vivid red, paints those years as bright and intense. Overall, the mood is nostalgic and tender, with sadness underneath the happiness, because the speaker can only revisit these days, not return to them.