Castanets are a percussion instrument (idiophone), used in Moorish, Ottoman, ancient Roman, Italian, Spanish and Portuguese music. The instrument consists of a pair of concave shells joined on one edge by a string. They are held in the hand and used to produce clicks for rhythmic accents or a ripping or rattling sound consisting of a rapid series of clicks. They are traditionally made of hardwood, although fibreglass is becoming increasingly popular. In practice a player usually uses two pairs of castanets. One pair is held in each hand, with the string hooked over the thumb and the ...

The 50s progression is a chord progression and turnaround used in Western popular music. As the name implies, it was common in the 1950s and early 1960s and is particularly associated with doo-wop. It has also been called the Ice-cream changes, the"Stand by Me" changes , and the doo-wop progression. The progression is: I vi IV V (see chord (music)#Roman numerals). For example, in C major: C Am F G (macro analysis). Theory In Western classical music during the common practice period, chord progressions are used to structure a musical composition. The destination of a chord progression is...

A blood donation occurs when a person voluntarily has blood drawn and used for transfusions or made into medications by a process called fractionation. In the developed world, most blood donors are unpaid volunteers who give blood for a community supply. In poorer countries, established supplies are limited and donors usually give blood when family or friends need a transfusion. Many donors donate as an act of charity, but some are paid and in some cases there are incentives other than money such as paid time off from work. A donor can also have blood drawn for their own future use. Don...