Sense #4 Taste
Stop licking the piano keys!
No, seriously...in order to use the sense "taste" in music, it does not mean literally tasting the piano keys or the music on the stand.
The sense of taste uses mainly the tongue, but the lips, hard and soft palates, teeth and gums are all part of the big picture. We use these same parts every time we talk and sing. I strongly encourage young pianists to sing or speak while they are playing. Some options would be to sing the words to the song, speak the words to the song (especially if they are self-conscious about their singing voice), speak the counts "1-2-3-4", speak the rhythm "quarter note, half note, whole note", or the letter names of the notes (if its a simple melody).
This also aids in matching pitch and reinforcing the melody of the song. So sing away!