The charts have seen many a one-hit wonder, but some musicians keep plugging away. The man who holds the longest note was then a vocalist with Tommy Dorsey, on "I'll Never Smile Again", No 1 in 1940 - Frank Sinatra. He holds a place in the latest Billboard album chart.
In 1940, Billboard was producing its own unified chart by asking what was selling well at 50 stores, including the Louis Pizitz Dry Goods Company, Atlanta. The early hit parade has evolved into today's hi-tech version, in which sales at record store tills are electronically passed down phone lines to the chart compilers.
The US chart does not merely tot up the sales. Added into the equation is the amount of airplay each record has received - and how many people were listening at the time. A sample of America's 11,500 radio stations is vetted by electronic "listeners" programmed to recognise a couple of snatches taken from a large number of new releases.
The Top 10 did not reach Britain until New Musical Express published its first sales chart, in 1952. This featured several names still shifting records today. The late Nat King Cole, recently exhumed for a duet with his daughter, was crooning away at No 3 with "Somewhere Along the Way". Vera Lynn, in her pre-Dame days, was at No 7 with "Forget Me Not". The public clearly didn't, because another of her songs was at No 9 and yet another at No 10. Frankie La(i)ne's "High Noon" shared the No 7 slot; he was also at No 8, this time in a duet with Doris Day.
In 1954, NME turned its Top 10 into a Top 20; other music publications started their own listings, which the BBC amalgamated into its grand list in 1955. Over much of the Sixties, the charts were swamped by the Beatles, who in January 1964 could boast six hits at the same time - one an album. Three months later they pulled off an even bigger coup in the US: Billboard's chart showed the Fab Four in the top five places.
In 1978 Paul McCartney, trading as Wings, was, with "Mull of Kintyre", the first to sell more than 2 million copies of a single in Britain. The biggest-selling single of the present decade is by Robson and Jerome, the singing soldiers. Their "Unchained Melody" was in its best week selling around 400,000 copies; normally a weekly sale of 100,000 is enough to push a title into the No 1 slot.
Their warbling may be old-fashioned, but the technology used to record their sales is not. Chart Information Network, which provides the figures for the Radio 1 Sunday afternoon UK Top 40, monitors 2,300 of the country's 3,000 record stores, totting up all sales until midnight on Saturday. In 1936 a hit record was something that went round at 78 rpm. Today the same main title can come out as a 7in or 12in vinyl, or as a cassette, or as a CD, each accompanied by different tracks or mixes. A title's sales in three of those four formats can be added together to count towards its final chart position.
Like NME, Billboard splits its charts by categories such as Rap, R'n'B, Dance, Country, Latin, Gospel or even "Top Contemporary Christian". Its bestselling 200 list of albums is based not on airplay but entirely on copies sold. Don't laugh at Frank Sinatra still being there: Ol' Blue Eyes at least has the advantage of being 100 per cent alive, unlike members of some of the groups also in the Top 200 - Nirvana, Queen and the Grateful Dead. And the Beatles are at No 1.