They were 20-somethings emboldened by new technology. If they were shrewd, they just might get rich.

These inventors and wheedlers, dreamers and hucksters, were making the all-powerful software apps of their day: popular songs, sold then as widely distributed sheet music and phonograph records. They even had something of an addictive 'Angry Birds' app back then: Irving Berlin.

More than a century from the birth of the modern music industry -- which coalesced around a few Manhattan blocks known as Tin Pan Alley -- a new generation of entrepreneurs has become entranced by the possibilities of software apps. Consumers have downloaded 30 billion iPhone and iPad apps to date, and Apple Inc. alone has already paid out $5 billion to these developers. It's all growing very, very fast.

Much separates the Sousa era from our Shazam moment. And yet the two somehow belong together, a prelude and coda in the clanging symphony of markets in action.

As with the songsters of earliest Tin Pan Alley, the apps business now is open to virtually anyone with a good idea. Then and now, mass audiences created the hope of quick, large profits. Then and now, success was rampantly cloned. Just as today's coders build Instagram knockoffs, songwriters of the 1910s pulled all-nighters ripping off a hit number.

Above all, the early music trade evolved to respond to the problem of marketing and distribution. There was always music in American life. The blocks around West 28th Street known as Tin Pan Alley perfected the craft of getting those songs in front of America's rapidly growing population. Melodies became the original viral app -- an entreaty to buy sheet music or a recording. As the saying went, a song 'was just a clever advertisement set to music.'

Soon, the young German emigres who ran Tin Pan Alley came to realize that having a great song didn't guarantee its future. A song had to be sold, or 'made,' by a network of song-pluggers who bribed and cajoled Vaudeville acts and hotel orchestras to play their tunes. At one point, the singer Al Jolson received a racehorse for performing a promoter's latest. Success 'was the result of a process of systematic, deliberate promotion,' says David Suisman, a University of Delaware professor and author of the excellent book 'Selling Sounds,' about the early music industry.

In today's market, it turns out that coding is the relatively easy part for apps-makers. Marketing and selling the app remains a crude undertaking. It's still difficult for users to discover new apps much beyond Apple's 'Top 10' lists. As in Tin Pan Alley, a mercenary world of gimmickry and 'hit-making' middlemen promise to push an app onto these charts. Song-plugging has even returned. Today it's called 'pay per install' -- in which app developers pay anywhere from a quarter to a few dollars for each app download.

'The barriers to entry are definitely increasing,' says 37-year-old Amos Marvel, the co-founder of Los Angeles-based Hidden Variable Studios, whose well-received game 'Bag It!' is number one on Apple's free-download charts. Unlike some developers, Mr. Marvel declined to pay to have the game reviewed by certain websites. He did launch a promotion that pushed the apps to users via a service called App-O-Day, which charges a fee for each user download.

Hidden Variable hasn't yet recovered its costs, Mr. Marvel says. He estimated it could take up to a year to earn it back. 'People don't realize how much marketing it takes to get in front of people.'

People in the apps business don't like to talk about a shakeout. In conversations with eight app developers, none eagerly endorsed the idea. But it's hard not to come away feeling that just such a winnowing is near. Apple alone has 640,000 apps on its website. The lists for just the top-rated 'puzzle games' in the App store number 420. One recent developer survey found that four in five don't generate enough revenue to support a stand-alone business.

Venture capitalist Matt Murphy at Kleiner Perkins Caufield & Byers runs a $200 million fund that invests in promising apps. The apps market may be evolving, but the pay-per-install middlemen look here for now. There is no way to 'efficiently spend marketing dollars in mobile,' he says.

Typical costs now run roughly $1.50 to $1.80 per installation, a stiff sum for a free or 99-cent app. Games companies are now spending 60% to 70% of their gross income on this marketing, he says.

For companies that can then make money on 'in-app' purchases, the rewards still entice. A single hit game, he says, can make $2 million per month.

'I don't worry about a shakeout,' he ads. 'A great product can do pretty well.'

Like any marketplace, the power of scale, expertise, and efficiency will eventually exert itself. It happened in Tin Pan Alley, where by the 1910s, the industry became ruthlessly specialized, with buildings along 28th Street packed with professional songwriters, musicians, and sales jockeys. Competition had earlier reduced sheet music to a mere penny a copy. The industry had to rationalize to keep growing.

Such is the proposition of games-maker Zynga Inc., which in March spent $200 million for the company that built a game called Draw Something. Putting it in front of Zynga's 292 million users instantly created value. 'Once centers of gravity form it's hard to pull users away,' says Paul Bettner, who built the 'With Friends' games franchise, which later sold to Zynga in 2010.

Tin Pan Alley songwriters soon understood the ruthlessness of their jobs inside this new cultural machine. For the vast majority, success felt like a lottery. As one publisher admitted, there just was 'not much profit in song-writing.'

MARKETING & DISTRIBUTION: Hired 'song pluggers' to sing songs in public, while making payments to top Vaudeville performers. Eventually gave birth to the 'payola' system of radio.

MAKING IT A HIT: Mimic a popular song, often by subtle tweaks in title or song chorus.

HARDWARE & SOFTWARE: Victor Talking Machine Co. constantly updated its record releases, largely focusing on opera singers such as Enrico Caruso. Selling records helped sell record players.

MARKETING & DISTRIBUTION: Hire 'pay-for-install' companies that guarantee installations of new apps. It is also possible to pre-buy a number of lowerquality downloads to push an app atop Apple's charts.

MAKING IT A HIT: Mimic a popular game or utility app, often by subtle tweak of features or game characters.

HARDWARE & SOFTWARE: Apple regularly updates software offerings and iTunes music and video store. Selling media helps sells iPads and iPhones.