The frontpiece of E. E. Fournier D’Albe’s 1924 The Moon-Element: An Introduction to the Wonders of Selenium is a picture of him, on the left, and the first iteration of the optophone in 1912:

In those years around 1912 Fournier D’Albe (1868-1933) was working in Oliver Lodge’s laboratory in Birmingham. He repeatedly noted the interest and support of Lodge in his research and, indeed, there is a notable influence of Lodge in The Moon-Element itself. Namely, Fournier D’Albe combines Lodge’s notion of an all-conveying medium of ether with the possibility of the transformation or metamorphosis of the human senses.

In the year 1910 the Author was appointed Assistant-Lecturer in Physics in the University of Birmingham. (…) With the active encouragement of the [physics] Professor¹ as well as the Principal of the University (Sir Oliver Lodge)², the Author started a research [program] on the properties of selenium (…) He [the Author] particularly investigated the manner in which selenium violates Ohm’s law…³

The element selenium (from Greek σελήνη, moon, discovered 1817) has its name due to its perceived relation to tellurium (from Latin tellus, earth, discovered 1782). Strangely, as set out by Fournier D’Albe, it was discovered only much later (in 1873) that selenium, like the moon, has a marked receptivity to light. And this, in the case of selenium, even when the light source is at a fantastic distance from it.

the Moon-element is unsurpassed in its function of producing [variable] electric currents from [variable] light. It is the supreme bridge between [these] two of the most vital forms of energy.⁴ 

This gave Fournier D’Albe the notion of

utilisation of the action of light on selenium for the purpose of recording star transits. He [the Author] succeeded in making Aldebaran [located at 65 light years from Earth!], a first-magnitude star,⁵ ring a bell in its passage across the meridian.⁶  (…) The fact that light could be made to ring a bell [in this way] showed conclusively that in one respect, at least, the ear could be substituted for the eye.⁷

The twin actions at stake here, the conversion of light to sound and the implicated conversion to eyesight to ear-hearing could both be considered as enabled by the medium of Lodge’s “ether”:

The influences [like light or magnetism] thus exerted “across space” (…) irresistibly suggest that there must be a medium through which they are propagated, a medium whose properties  determine that speed of propagation. This hypothetical medium is called [notably by Lodge.] “the ether of space”. Every movement of an electric charge, whether it consists of electrons, protons, larger ions, or charged bodies, sets up some sort of “strain” in the ether, which is propagated in all directions with the speed of light.⁸

It is just as if every electron were connected with every other by invisible elastic fibres, so that none of them could start in any direction without the help of all the rest.⁹

Fournier D’Albe then got the idea got the idea that an analogous set up might allow the blind to read through the selenium enabled conversion of reflected light from a page of print into musical tones.

our optical resources, which for centuries have developed along the same grooves, are capable of entirely new departures.¹⁰

Sight had been extended since Galileo through analog means or “grooves” by devices that sharpened focus or gathered more light. Now Fournier D’Albe was suggesting a digital means of extension through conversion. Such a revolution would soon overtake everything from wristwatches on up. 

Last year (1912) I described and exhibited at the London Optical Convention an apparatus for converting light into sound by means of electrical effects, and proposed the name ‘optophone’ for such an instrument, as its primary object is not to transmit sound by means of light (photophone)¹¹ but to ‘see’ by means of sound.¹²

This was to “read by the ear”.¹³ “The form of each letter causes it to sing its own little tune.”¹⁴  

Since the number of books (not to speak of newspapers, magazines, journals, invoices, etc) in print is enormously greater than these in brail, the potential benefit to the blind was very great.

We shall have “converted light into sound” through the medium of an electric current. That this “conversion” is symbolical rather than actual is evident when we consider the enormous disproportion of sound-waves and light-waves. Sound-waves are measured in feet, and are represented by the lengths of organ pipes. Light-waves are from forty thousand to seventy thousand to the inch, according to their colour.¹⁵

By “symbolical” Fournier D’Albe meant that sound and light were not continuous on each other as physical phenomena. They were not analog. Instead they were definitively discrete¹⁶ and yet were convertible, presumably via the fundamental enabling action of “the ether of space”.¹⁷

Today we know the name of this “space” or pervading power: digitality.