From the given text, write some important points about guitar's vibrato system

1. A vibrato system is a mechanical component that alters the pitch of the strings on a guitar.
2. They modify the string tension at the bridge or tailpiece of an electric guitar using a regulating lever, sometimes known as a whammy bar, vibrato bar, or wrongly as a tremolo arm, to add vibrato to the music.
3. With the help of the lever, the musician can quickly and momentarily alter the tension and occasionally the length of the strings, which alters the pitch and produces effects such as vibrato, portamento, and pitch bend.
4. Vibrato-free instruments need different bridge and tailpiece systems.