Like any plucked instrument, mandolin notes decay to silence rather than sound out continuously as with a bowed note on a violin, and mandolin notes decay faster than larger stringed instruments like the guitar. This encourages the use of tremolo (rapid picking of one or more pairs of strings) to create sustained notes or chords. The mandolin's paired strings facilitate this technique: the plectrum (pick) strikes each of a pair of strings alternately, providing a more full and continuous sound than a single string would.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What happens to mandolin notes when plucked? 
Ah, so.. decay to silence

Cetaceans were historically abundant around the island as commercial hunts on the island was operating until 1956. Today, numbers of larger whales have disappeared, but even today many species such humpback whale, minke whale, sei whale, and dolphins can be observed close to shores, and scientific surveys have been conducted regularly. Southern right whales were once regular migrants to the Norfolk hence naming the island as the "Middle ground" by whalers, but had been severely depleted by historical hunts, and further by illegal Soviet and Japan whaling, resulting in none of very few, if remnants still live, right whales in these regions along with Lord Howe Island.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What other species can be seen close to the shores of Norfolk Island?
Ah, so.. dolphins

In July 1943, as a result of the American Federation of Musicians boycott of US recording studios, the a cappella vocal group The Song Spinners had a best-seller with "Comin' In On A Wing And A Prayer". In the 1950s several recording groups, notably The Hi-Los and the Four Freshmen, introduced complex jazz harmonies to a cappella performances. The King's Singers are credited with promoting interest in small-group a cappella performances in the 1960s. In 1983 an a cappella group known as The Flying Pickets had a Christmas 'number one' in the UK with a cover of Yazoo's (known in the US as Yaz) "Only You". A cappella music attained renewed prominence from the late 1980s onward, spurred by the success of Top 40 recordings by artists such as The Manhattan Transfer, Bobby McFerrin, Huey Lewis and the News, All-4-One, The Nylons, Backstreet Boys and Boyz II Men.[citation needed]
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What gained renewed intrest the 1950's?
Ah, so..
unanswerable