Alexander Graham Bell famously unveiled the telephone to the public on May 10, 1876, before members of the American Academy of Arts and Sciences at the Boston Athenaeum. If you stand before the venerable stone building today, it is easy to conjure the scene of gentlemen in top hats emerging from horse-drawn carriages and streaming toward the meeting to hear a young scientist present what he called his “researches in telephony.” He took the opportunity to describe his work and trace the efforts of his predecessors to send sounds over telegraph wires; as he wrote to his parents immediately afterward, “the meeting at the Academy was a grand success.”

But a close look at primary documents, including Bell’s detailed letter home and the text of his talk that survives in the leather-bound Proceedings of the American Academy, reveals something curious. Bell, who had successfully called to his assistant Thomas Watson over a telephone two months earlier and had also secured a broad U.S. patent on the invention, did not use this public debut to show how the device could transmit speech. He demonstrated to his colleagues only the far lesser technological feat of transmitting simple musical tones, something a number of researchers had already accomplished. As Bell told his parents, he strung telegraph wires from his office down the street to the Athenaeum and had an assistant send “some rich chords” from what he described as a “telegraphic organ” in his office.

It was two weeks later, before a good-sized audience at a meeting of the MIT faculty, that Bell publicly unveiled the most exciting aspect of his research. Handwritten minutes from the Institute Archives reveal that Bell carried on an unprecedented public conversation over the newfangled contraption. The specific words are, sadly, lost to history. A brief Boston Transcript article about the event noted that vowel sounds came through Bell’s telephone intelligibly enough, while consonants were all but “unrecognizable.” The article went on to say that “occasionally, however, a sentence would come out with startling distinctness.”

The choice of MIT as the venue for the worldwide introduction of Bell’s speaking telephone couldn’t have been more fitting. It reflects a little-known fact of telephone history: MIT professors and equipment had played a key role in Bell’s work.

Bell, a native of Edinburgh, Scotland, had landed in Boston in 1871 in his early 20s, hoping to invent things in his spare time. A teacher of the deaf and the son and grandson of elocutionists, he had a strong working knowledge of acoustics and speech but little solid training in mathematics or physics. In Boston, however, he found himself at the world’s center of telegraphic research.

A particular hub for visionary inventors of all sorts was the Charles Williams machine shop on Court Street, where almost all of Bell’s earliest telegraphic devices were constructed. The ­Williams shop, which built prototypes for many top inventors of the period, employed roughly two dozen machinists, including the young Thomas Watson, whom Bell eventually hired. In his autobiography, Watson described it as a “thrilling place” buzzing and clattering with the din of lathes and metalworking tools as workers turned out an array of strange new electrical devices, from telegraph relays to galvanometers. Even young Thomas Edison set up a lab above the shop so he could easily avail himself of its services. There, before Bell’s arrival in Boston, Edison had won his very first patent, in 1869–for an electrical vote recorder.

In 1872, Bell started attending MIT’s public lectures on experimental mechanics, including one in October by Professor Charles R. Cross that began a long, fruitful collaboration. At the talk, Cross demonstrated a device invented by his colleague Edward C. ­Pickering, who then chaired MIT’s physics department. Pickering’s so-called tin-box receiver had a thin metal diaphragm that vibrated when a current passing through an electromagnet was interrupted. As a result, it could crudely reproduce, on the other end of a telegraph line, the sound of a tuning fork rigged so that its vibrations would make and break a battery-­powered electrical circuit.

No one had yet conceived of how to translate the sound waves from the human voice into an electrical current, and Pickering’s primitive receiver couldn’t even have emitted them. (That part of the telephone puzzle–the design of the transmitter–makes up the mystery at the heart of my 2008 book, The Telephone Gambit.) Nonetheless, Pickering was one of the very first to develop a device that could pick up musical tones sent over telegraph wires. Bell was already keenly interested in this subject, and the exposure to Pickering’s research surely spurred on his labors.

At the time of Cross’s lecture, MIT (which had been incorporated in 1861 on the Boston side of the Charles River) had recently opened the Rogers Laboratory of Physics in a new building on Boylston Street. The facility was the first of its kind in the United States, a well-outfitted working laboratory that allowed students to conduct experiments illustrating the physical laws they learned about in class. Of particular interest to Bell, the new laboratory had an impressive set of equipment identical to that used in the pathbreaking work of Hermann von Helmholtz, one of the world’s leading acoustical researchers.

In 1873, Bell accepted a position as a professor of vocal physi­ology and elocution at the fledgling Boston University (which had been chartered in 1869). The post drew him into even closer contact with Boston’s scientific community, affording him the chance to get better acquainted with Professor Cross, who would eventually succeed Pickering as chair of MIT’s physics department.

In April 1874, after Bell addressed MIT students and faculty about his acoustical studies and his efforts to teach the deaf to speak, Cross–apparently impressed–granted him unfettered access to the Institute’s facilities for his further research. Bell seized the opportunity. In May, he wrote to his parents about working at MIT with Cross in pursuit of an improved “phonautograph,” a device creating a precise visual representation of different vocal sounds.

Over the next several years, Bell discussed a variety of scientific matters with Cross and sought his advice on numerous occasions. Some of the most detailed information about the work Bell did at MIT comes from depositions he and others made for lawsuits challenging his ownership of the telephone idea–lawsuits that continued for nearly two decades after he patented the device.

To hold onto his broad U.S. patent on the telephone, Bell downplayed the debt he owed to other inventors. In court, for instance, Bell claimed that he didn’t remember much about the work of German inventor Philipp Reis, who by many accounts developed a working telephone as early as 1861, when Bell was still a teenager. But there is evidence to contradict Bell’s claim. Not only did he cite Reis’s work in his lecture to the American Academy, but Cross recalled under oath that he had personally spoken to Bell about Reis’s telephone as early as the spring of 1874–nearly two years before Bell’s telephone patent. In one of the incidents Cross recounted, a very excited Bell had come to him with an idea for what he believed was a new type of receiver, only to have Cross explain that Reis had already invented it. Although Cross never explicitly implicated Bell in wrongdoing, he testified that he had fully explained Reis’s telephone device to Bell on two occasions.

Of course, Bell won his patent claim as the sole inventor of the telephone, and public knowledge about the contributions of others mostly faded into oblivion. The many surviving primary documents from the period, however, leave little doubt of the important supporting role that Cross and the Rogers Laboratory played in helping Bell gain vital, detailed, and often hands-on knowledge about the cutting-edge work of others in the field, including ­Pickering, Helmholtz, Reis, and Elisha Gray, the inventor whose pathbreaking design for a liquid transmitter Bell seems to have appropriated to make his world-famous call to Watson.

Many years later, with Bell’s legal claim to the telephone long since secured, he publicly acknowledged Cross’s contribution. Bell told the crowd of 1,500 assembled at Symphony Hall for MIT’s 50th-anniversary gala–and more than 5,000 alumni and guests who were listening in by phone at Alumni Association gatherings across the country–that Cross had not only made “many advances in the telephone itself” but inspired many students to “go forth from the Institute to perfect the work.”