There can be several reasons why a song may suddenly sound different to you:
Perception and Mood: Your perception of music can be influenced by your current mood, emotions, and mindset. If you're feeling happy, a song may sound more upbeat and enjoyable, while if you're feeling down, the same song might seem more melancholic or even irritating.
Listening Environment: The environment in which you listen to a song can impact your perception of it. If you're in a noisy or distracting environment, you might not be able to fully appreciate the nuances of the music. On the other hand, a quiet and serene setting can enhance your listening experience.
Familiarity: The more you listen to a song, the more familiar it becomes. This familiarity can lead to different perceptions over time. Sometimes, repeated listens can make a song feel stale, while other times it can deepen your appreciation for the subtleties in the music.
Personal Experiences: Your personal experiences and memories associated with a song can significantly alter how you perceive it. If a song reminds you of a happy memory, it might evoke positive feelings, while a song linked to a sad event might trigger negative emotions.
Changes in Taste and Preferences: Your taste in music can evolve over time. What you enjoyed in the past might not resonate with you as strongly now. As your preferences change, songs you once loved may no longer have the same impact.
Physiological Factors: Physical factors such as fatigue, stress, or illness can affect how you perceive and interpret sound. When you're tired or unwell, your ability to enjoy music may be compromised.
Musical Knowledge: As you gain more musical knowledge and experience, you might start noticing aspects of songs that were previously unnoticed. This enhanced understanding can alter your perception and appreciation of music.
Changes in the Song Itself: Sometimes, a song may actually be re-recorded, remixed, or remastered, resulting in a different version being played. Such changes can make the song sound different to what you're used to.
In conclusion, music is a highly subjective and dynamic experience. Your perception of a song can be influenced by a multitude of factors, and it's entirely normal for a song to sound different to you at various times in your life.