Singing is the act of producing musical sounds with the voice, and augments regular speech by the use of both tonality and rhythm. A person who sings is called a singer or vocalist. Singers perform music known as songs that can either be sung a cappella or accompanied by musicians and instruments ranging from a single instrumentalist to a full symphony orchestra or big band. 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. Nearly anyone who can speak can sing, since singing resembles sustained speech.

Singing can be informal and done for pleasure; for example, singing in the shower or karaoke; or it can be very formal, as in the case of singing during a religious ritual such as a Mass or professional singing performances done on stage or in a recording studio. Singing at a high amateur or professional level usually requires 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 a voice teacher or vocal coach throughout their career.

In many modern pop musical groups, a lead singer performs the primary vocals or melody of a song, as opposed to a backing singer who sings backup vocals or the harmony of a song. Backing vocalists sing some, but usually not all, parts of the song often singing only in a song's refrain or humming in the background. An exception is five-part gospel a cappella music, where the lead is the highest of the five voices and sings a descant, and not the melody. Some artists may sing both lead and backing vocals on audio recordings by overlapping recorded vocal tracks.

Popular music includes a range of vocal styles. Hip-hop uses rapping, the rhythmic delivery of rhymes in a rhythmic speech over a beat or without accompaniment. Some types of rapping do are mostly or entirely comprised of speech and chanting, like the Jamaican "toasting" from which rapping derives historically. In some types of rapping, the performers may interpolate short sung or half-sung passages. Blues singing is based on the use of the blue notes–notes sung at a slightly lower pitch than that of the major scale for expressive purposes. In heavy metal and hardcore punk subgenres, vocal styles can include techniques such as screams, shouts, and unusual sounds such as the "death growl".