What does the term "A tempo" instruct a performer to do?

The term "A tempo" is a musical instruction that tells the performer to return to the original tempo after a deviation from it. In a piece of music, the tempo may change for various reasons, such as expressive phrasing or technical demands. "A tempo" serves as a reminder to go back to the speed established at the beginning of the piece or section, helping to maintain the intended feel and structure of the music. This instruction is crucial for ensuring that the performance remains cohesive and maintains the composer's original intent regarding timing and pacing.