CD in the context of "Roud Folk Song Index"

A library is a collection of books, and possibly other materials and media, that is accessible for use by its members and members of allied institutions. Libraries provide physical (hard copies) or digital (soft copies) materials, and may be a physical location, a virtual space, or both. A library's collection normally includes printed materials which can be borrowed, and usually also includes a reference section of publications which may only be utilized inside the premises. Resources such as commercial releases of films, television programmes, other video recordings, radio, music and audio recordings may be available in many formats. These include DVDs, Blu-rays, CDs, cassettes, or other applicable formats such as microform. They may also provide access to information, music or other content held on bibliographic databases. In addition, some libraries offer creation stations for makers which offer access to a 3D printing station with a 3D scanner.

Libraries can vary widely in size and may be organised and maintained by a public body such as a government, an institution (such as a school or museum), a corporation, or a private individual. In addition to providing materials, libraries also provide the services of librarians who are trained experts in finding, selecting, circulating and organising information while interpreting information needs and navigating and analysing large amounts of information with a variety of resources. The area of study is known as library and information science or studies.

Optical disc packaging is the packaging that accompanies CDs, DVDs, and other formats of optical discs. Most packaging is rigid or semi-rigid and designed to protect the media from scratches and other types of exposure damage.

MPEG-4 is a group of international standards for the compression of digital audio and visual data, multimedia systems, and file storage formats. It was originally introduced in late 1998 as a group of audio and video coding formats and related technology agreed upon by the ISO/IEC Moving Picture Experts Group (MPEG) (ISO/IEC JTC 1/SC29/WG11) under the formal standard ISO/IEC 14496 – Coding of audio-visual objects. Uses of MPEG-4 include compression of audiovisual data for Internet video and CD distribution, voice (telephone, videophone) and broadcast television applications. The MPEG-4 standard was developed by a group led by Touradj Ebrahimi (later the JPEG president) and Fernando Pereira.

Loud music is music that is played at a high volume, often to the point where it disturbs others and causes hearing damage. It may include music that is sung live, played with musical instruments, or with electronic media, such as Radio broadcasting, CD, MP3 players or even on phones and streaming services.

Playing loud music that can be heard by others in nearby properties is considered rude by many societies in many settings, and may result in loss of respect and legal action under the nuisance ordinance. In certain contained settings, such as nightclubs or concerts, music is often played very loudly, but is viewed as acceptable. Headphones allow loud music to be enjoyed without annoying neighbors, though leakage is an issue with headphones, and the listener will still get hearing damage.

Cover art is a type of artwork presented as an illustration or photograph on the outside of a published product, such as a book (often on a dust jacket), magazine, newspaper (tabloid), comic book, video game (box art), music album (album art), CD, videotape, DVD, or podcast. Cover art can include various things such as logos, symbols, images, colors, or anything that represents what is being sold or advertised. The art has a commercial function (i.e., to promote the product it is displayed on), but can also have an aesthetic function, and may be artistically connected to the product (such as with art by, or commissioned by, the creator of the product).

Optical engineering is the field of engineering encompassing the physical phenomena and technologies associated with the generation, transmission, manipulation, detection, and utilization of light. Optical engineers use the science of optics to solve problems and to design and build devices that make light do something useful. They design and operate optical equipment that uses the properties of light using physics and chemistry, such as lenses, microscopes, telescopes, lasers, sensors, fiber-optic communication systems and optical disc systems (e.g. CD, DVD).

Optical engineering metrology uses optical methods to measure either micro-vibrations with instruments like the laser speckle interferometer, or properties of masses with instruments that measure refraction.

Live PA (meaning live public address or live personal appearance) is the act of performing live electronic music in settings typically associated with DJing, such as nightclubs, raves, and more recently dance music festivals.

In a performative context, the term was originally used to refer to live appearances, initially at rave events in the late 1980s, of studio based producers of electronic dance music who released music using fixed media formats such as 12-inch single, CD, or music download. The concept of the live PA helped provide a public face for a scene that was criticized as "faceless" by the mainstream music press. The trend was quickly exploited by a music industry desperate to market dance music to a popular audience.