"Con sordino" is a musical term that refers to a technique in which a musician plays with a mute, resulting in a softer, more muted sound. There are a few synonyms that can be used to describe the same effect, including "with a mute", "muted", and "damped". Each of these terms can be used to convey the same idea of lowering the volume and reducing the brightness of the sound, creating a more subdued and intimate tone. Other similar terms might include "hushed" or "subdued", which have a similar effect of quieting the sound and creating a more intimate atmosphere.