By Elijah Wald, Globe Correspondent, 11/14/99

n the early 1980s, Tracy Chapman used to sing on the sidewalk in Harvard Square. She did not use any amplification, and you could hear her voice a block away, rich and clear, despite the traffic. It was probably the last time an audience has had a chance to hear how a major non-classical singer actually sounds.

These days, terms like ''acoustic music'' have become a sort of Orwellian newspeak. ''MTV Unplugged,'' for example, features rock stars who, rather than playing electric guitars plugged into sound-amplifying devices, play acoustic guitars plugged into sound-amplifying devices. Their plugged-in-ness excites no comment, because it has been decades since anyone in the pop music world has let an audience hear how he or she sounds unmediated by electronics.

Amplification has been, along with recording, the most significant agent of change in 20th-century music. It turned the guitar from a background, rhythm instrument into the most popular lead instrument in the world. It made it possible for a trio or quartet of musicians to make more noise than a big band. And it changed singing completely.

In the old days, the first demand of musical performance was projection. Tone, phrasing, attack, pitch, and soul were important, but first you had to make yourself heard. The high, nasal, singing common in American country music, and in folk styles around the world, is a direct result of this need: It is the easiest way to make one's voice carry over a distance. The bel canto style of European opera or the shouting style of African-American gospel music are more technically demanding ways of solving the same problem.

The first microphones were invented in the early 19th century, but it was a hundred years before they were commonly used to amplify music. One can hear the effects of their arrival on records from the 1930s and 1940s. The older singers have big, solid voices, but the new wave in jazz, pop, and blues comprises ''crooners,'' singers who perform in some approximation of a normal speaking voice.

Vocal marvels like Joe Turner could shout unamplified over a full horn band in a crowded club, but the average big-band vocalist would have been inaudible without electronic assistance. Then, by the late 1940s, the big band itself had succumbed to the new technology: When club owners realized that three or four electrically enhanced players could please an audience, they saw no more reason to pay 20 musicians.

Once amplification had become the norm for popular stars, it was gradually adopted by everyone else, whether or not it was needed. While classical soloists play unamplified cello or flute and can be heard from the top rear balcony of Symphony Hall, folk clubs regularly amplify full bands playing for an audience of 30 or 40 people.

Electricity created a new generation of instruments, first the theremin and then all the various keyboard instruments, the electric guitar (which in Hendrix's hands went way beyond being simply an amplified guitar), and the multifarious arrivals of the computer age. At the same time, though, it produced a new laziness. Singers no longer need learn how to sing, and an audience no longer has to put any effort into listening. When CDs first arrived, rereleases of acoustic music from LP often sounded dreadful, in part because the engineers doing the remastering had no idea how an unamplified violin or a guitar sounded.

In the end, the most profound effect of amplification may have been in making us forget that music is something that can happen unmediated by technology. Musicians pride themselves on doing live shows that sound as cleanly produced as a studio recording - as if live sound was not the original product, but only a road-show imitation. And the ordinary human voice, the oldest of all instruments, is almost never heard.

This story ran on page L04 of the Boston Globe on 11/14/99.
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