Fundamental bass refers to the lowest note in a musical chord, which serves as the foundation for harmony. It is typically played by the bass instruments in an ensemble, such as the double bass or tuba, and is crucial for establishing the tonal center of a piece. In music theory, the fundamental bass can also relate to the concept of figured bass, where numbers and symbols indicate the intervals above the bass note that should be played. This practice was common in the Baroque period, allowing musicians to improvise harmonies based on the written bass line.