This paper introduces the concept of synthesis based on performance sampling. It explains that although sampling has been considered a way to capture and reproduce the sound of an instrument, it should be better considered a way to model the sonic space produced by a performer with an instrument. The paper presents a singing voice synthesizer, pointing out the main issues and complexities emerging along its design. Although the current system is able to generate convincing results in certain situations, there is still much room for improvements, especially in the areas of expression, spectral modeling and sonic space design. However, computer singing is definitely coming close to becoming indistinguishable from human performances.