There could be several reasons why your piano playing might sound messy, even if you're not making many mistakes. Here are a few possible explanations:
Technique: Playing the piano involves more than just hitting the right keys. Proper technique is essential for producing a clean and balanced sound. Focus on maintaining a relaxed hand position, using the correct fingerings, and employing a consistent and controlled touch on the keys.
Dynamics and expression: Expressiveness is crucial in piano playing. Pay attention to the dynamics (volume) of your playing, and vary them appropriately to bring out the musical phrases. Utilize legato (smooth) and staccato (short and detached) touches as needed to create musical contrast.
Pedaling: The piano pedal is an important tool for achieving a rich and connected sound. Be mindful of how and when you use the pedal. Experiment with different pedal techniques, such as half-pedaling or selective pedaling, to enhance the clarity and texture of your playing.
Timing and rhythm: Even if you're playing the correct notes, imprecise timing or rhythm can contribute to a messy sound. Practice with a metronome or play along with recordings to develop a strong sense of timing and rhythmic accuracy.
Voicing and balance: When playing music with multiple voices or chords, it's essential to balance the sound appropriately. Ensure that the melody or main voice stands out while the accompanying voices provide a supportive foundation. Work on controlling the volume and emphasis of different parts simultaneously.
Instrument condition: If your piano is not properly maintained, it may affect the sound quality. Consider having your piano tuned regularly by a professional technician to ensure that it's in optimal condition.
Remember, developing good piano technique and musicality takes time and practice. Consider seeking guidance from a piano teacher or instructor who can offer personalized feedback and help you address specific issues you may be facing in your playing.