The e-Sax Whisper Mute System is the only saxophone mute that allows you to play at full volume while outside the case only a whisper can be heard. Monitor your actual sound (dynamics, timbre, etc.) via the ingenious pickup system and headphones. Practice in a hotel, in your home, or even warm-up back stage during a performance. The e-Sax Mute also proves an excellent recording tool when the out lines are plugged directly into a recording device. The line in feature allows you to play along with a CD or karaoke style.