Music lessons are a type of formal instruction in playing a musical instrument or singing. Typically, a student taking music lessons meets a music teacher for one-on-one training sessions ranging from 30 minutes to one hour in length over a period of weeks or years. For vocal lessons, teachers show students how to sit or stand and breathe, and how to position the head, chest, and mouth for good vocal tone. For instrument lessons, teachers show students how to sit or stand with the instrument, how to hold the instrument, and how to manipulate the fingers and other body parts to produce tones and sounds from the instrument. Music teachers also assign technical exercises, musical pieces, and other activities to help the students improve their musical skills. While most music lessons are one-on-one (private), some teachers also teach groups of two to four students (semi-private lessons), and, for very basic instruction, some instruments are taught in large group lessons, such as piano and acoustic guitar. Since the widespread availability of high speed. low latency Internet, private lessons can also take place through live video chat using webcams, microphones and videotelephony online.