Slow-wave sleep

Slow-wave sleep (SWS), often referred to as deep sleep, consists of stage three of non-rapid eye movement sleep, according to the Rechtschaffen & Kales (R & K) standard of 1968. There is not a clear distinction between stages three and four. Stage three has 20-50 percent delta activity, whereas stage four has more than 50 percent. As of 2008, the American Academy of Sleep Medicine (AASM) has discontinued the use of stage four, such that the previous stages three and four now are combined as stage three. An epoch (30 seconds of sleep) which consists of 20% or more slow-wave (delta) sleep, now is considered to be stage three.

This period of sleep is called slow-wave sleep because the EEG activity is synchronized, producing slow waves with a frequency of less than 1 Hz and a relatively high amplitude. The first section of the wave signifies a down state, which is an inhibition period in which the neurons in the neocortex are silent. This is the period when the neocortical neurons are able to rest. The second section of the wave signifies an up state, which is an excitation period in which the neurons fire briefly at a high rate. The former state is a hyperpolarizing phase and the latter is a depolarizing phase. The principal characteristics during slow-wave sleep that contrast with REM sleep are moderate muscle tone, slow or absent eye movement, and lack of genital activity.

Music

Music is an art form and cultural activity whose medium is sound and silence. The common elements of music are pitch (which governs melody and harmony), rhythm (and its associated concepts tempo, meter, and articulation), dynamics (loudness and softness), and the sonic qualities of timbre and texture (which are sometimes termed the "color" of a musical sound). Different styles or types of music may emphasize, de-emphasize or omit some of these elements. Music is performed with a vast range of instruments and with vocal techniques ranging from singing to rapping, and there are solely instrumental pieces, solely vocal pieces and pieces that combine singing and instruments. The word derives from Greek μουσική (mousike; "art of the Muses"). In its most general form, the activities describing music as an art form include the production of works of music (songs, tunes, symphonies, and so on), the criticism of music, the study of the history of music, and the aesthetic examination of music. Ancient Greek and Indian philosophers defined music as tones ordered horizontally as melodies and vertically as harmonies. Common sayings such as "the harmony of the spheres" and "it is music to my ears" point to the notion that music is often ordered and pleasant to listen to. However, 20th-century composer John Cage thought that any sound can be music, saying, for example, "There is no noise, only sound."

Deep Sleep

Deep Sleep is a 2012 point-and-click adventure game by Scriptwelder. It is a free browser game in which players attempt to navigate a dream world inhabited by shadow people. It was designed for and won first place in the 2012 Jay Is Games Casual Gameplay Design Competition.

Game Plot

Interested in lucid dreams, a researcher constructs a world in his mind to explore. However, the world in his dream quickly turns nightmarish, and the researcher becomes trapped. He needs to wake up, which is explained when the player finds a telephone saying he "must wake up". Shadowy figures haunt this world and attempt to restrict the player from guiding the researcher to freedom. At the beginning of the game, the player appears to be in a bedroom. To escape, the player must first find a key, then go into the next room and use the key on a locker. A cube with a keyhole in it appears, and the walls of the room melt down. The player will then have to explore his or her surroundings, and use acquired items to escape. The main obstacle in the game are locked doors, and cannot be opened unless certain items are acquired. After a long period of time, the player finally escapes the building he is in, but still has not woken up yet. Near the end of the game, shadowy figures start to appear and will advance towards the player. The player will then have to escape, as it is impossible to kill them. Running away, the player reaches a lighthouse with a Shadow Figure inside. The player then turns the light so it directly faces the Shadow Figure, and it vanishes. The game then ends, as the player "wakes up". However, the character is curious about the Shadow Figures he encountered and declares that he wants to visit them again.

Sleep

Sleep is a naturally recurring state of mind characterized by altered consciousness, relatively inhibited sensory activity, inhibition of nearly all voluntary muscles, and reduced interactions with surroundings. It is distinguished from wakefulness by a decreased ability to react to stimuli, but is more easily reversed than the state of hibernation or of being comatose. Mammalian sleep occurs in repeating periods, in which the body alternates between two highly distinct modes known as non-REM and REM sleep. REM stands for "rapid eye movement" but involves many other aspects including virtual paralysis of the body.

During sleep, most systems in an animal are in an anabolic state, building up the immune, nervous, skeletal, and muscular systems. Sleep in non-human animals is observed in mammals, birds, reptiles, amphibians, and fish, and, in some form, in insects and even in simpler animals such as nematodes. The internal circadian clock promotes sleep daily at night in diurnal species (such as humans) and in the day in nocturnal organisms (such as rodents). However, sleep patterns vary widely among animals and among different individual humans. Industrialization and artificial light have substantially altered human sleep habits in the last 100 years.

Instrumental

An instrumental is a musical composition or recording without lyrics, or singing, although it might include some inarticulate vocal input; the music is primarily or exclusively produced by musical instruments.

In a song that is otherwise sung, a section not sung but played with instruments can be called an instrumental interlude. If the instruments are percussion instruments, the interlude can be called a percussion interlude. These interludes are a form of break in the song.

In popular music

In commercial popular music, instrumental tracks are sometimes renderings of a corresponding release that features vocals, but they may also be compositions originally conceived without vocals. An instrumental version of a song which otherwise features vocals is also known as a -1 (pronounced minus one).

The opposite of instrumental music is a cappella.

For genres in which a non-vocal song or interlude is conceived using electronic media, rather than with true musical instruments, the term instrumental is nonetheless used for it.