The answer is `quality only`. This is because when the same note is played on different instruments, such as a sitar and flute, the pitch and loudness of the note will be the same. Pitch refers to the perceived frequency of a sound, essentially how high or low we perceive the sound to be, while loudness refers to the volume or amplitude of the sound, essentially how loud or soft we perceive the sound to be. Since the same note is played on both instruments, the pitch and loudness will not vary.

Quality, also known as timbre, on the other hand, refers to the characteristics of a sound that allow us to distinguish it from other sounds, even when they have the same pitch and loudness. Timbre is influenced by factors such as the source of the sound and the different frequencies present in the sound. So, it is the quality or timbre of the sound that allows us to distinguish between the sound of the same note played on a sitar and a flute.