Singing is the act of producing musical sounds with the voice, and augments regular speech by the use of both tonality and rhythm. One who sings is called a singer or vocalist. Singers perform music known as songs that can be sung either with or without accompaniment by musical instruments. Singing is often done in a group of other musicians, such as in a choir of singers with different voice ranges, or in an ensemble with instrumentalists, such as a rock group or baroque ensemble. As in many respects human song is a form of sustained speech, nearly anyone able to speak can also sing. Singing can be formal or informal, arranged or improvised. It may be done for pleasure, comfort, ritual, education, or profit. Excellence in singing requires time, dedication, instruction, and regular practice. Professional singers usually build their careers around one specific musical genre, such as classical or rock. They typically take voice training provided by voice teachers or vocal coaches throughout their career.
Scientific studies suggest that singing can have positive effects on people's health. A preliminary study based on self-reported data from a survey of students participating in choral singing found perceived benefits including increased lung capacity, improved mood, stress reduction, as well as perceived social and spiritual benefits. However, one much older study of lung capacity compared those with professional vocal training to those without, and failed to back up the claims of increased lung capacity. Singing may positively influence the immune system through the reduction of stress. One study found that both singing and listening to choral music reduces the level of stress hormones and increases immune function. A multinational collaboration to study the connection between singing and health was established in 2009, called Advancing Interdisciplinary Research in Singing (AIRS).
Scholars agree that singing is strongly present in many non-human species. Wide dispersal of singing behavior among very different animal species (like birds, gibbons, whales, and humans) strongly suggests that singing appeared independently in different species. Currently there are about 5400 species of animals that can sing. At least some singing species demonstrate the ability to learn their songs, to improvise and even to compose new melodies. In some animal species singing is a group activity (see, for example, singing in gibbon families.)