There was an attempt in the 1850s onwards to build ``enharmonic'' instruments of all kinds with many more than 12 notes per octave. The ``even'' tempered octave had actually existed only since Bach's time. Before that, instruments were tuned to ``perfect'' or ``mean'' scales, and could therefore only be played in certain keys. Even tempering meant for instance that the third and fourth were not perfect intervals related to the harmonics, but an approximation so that each note was a ``semitone'' apart, there being 12 equally spaced semitones per octave. Enharmonic instruments attempted, on the other hand, to provide the perfect tuning for all keys in one instrument. This was doomed to failure, as the keyboard versions were very complicated - fretless string instruments however were much more practical for a sufficiently accomplished player with a very good ear. To put this into perspective, one has to remember that unequally tempered pipe organs, such as St. George's Hall, Liverpool, the largest of its day, were still being built in the 1850s and played by some of the best musicians of their time, such as W.T. Best. Since the harmonium was small in size and stayed in tune (and was possibly still a scientific novelty) it lent itself well to experimentation.
In his Appendix to the famous On the Sensations of Tone by Helmholtz  its translator, A.J. Ellis notes  but none of them meet the wants of the student. They are all too expensive and require so much special education to use that (with the exception of Mr. Colin Brown's) they have remained musical curiosities, some of them entirely unique. But there are two instruments which are cheap and which can be tuned so as to illustrate almost every point of theory, though they of course remain experimental instruments intended only to shew the nature of musical intervals, chords and scales, and not to play pieces of music except especially composed exercises... They are a specially tuned harmonium and English concertina. Reed instruments are far the best for experiments, because they give sustained notes posessing a large number of powerful upper partial tones, so that any deviations from just intonation are extremely conspicuous, painfully evident indeed on any harmonium tuned in equal temperament.
Karl Goldbach told me in Jan'2008 that Ellis also described an earlier enharmonic harmonium invented by himself and built by T.W. Saunders . In 1937 an American enterprise delivered an Ellis harmonium build in the USA .
Whilst not truly an enharmonic instrument, the transposing organ, piano or seraphine illustrated another idea of the time. Edward Barry of Soho Square, London was granted a British patent on 17/7/1855, number 1,607 which contained the following description. I insert in the body of each instrument five or more notes or sounds above the number of keys in the keyboard, whether higher or lower in pitch, as may be desired, and by a mechanical contrivance I cause the keys to act upon different notes or sounds in the body of the instrument, thereby raising or lowering the pitch of the entire instrument at pleasure, and obtaining what I have before termed the transposition effect. In other words the keyboard could be moved sideways.
In fact such sliding keyboards became rather common in French harmoniums intended for church use. I am not sure if they were invented independently from the Barry patent.
Robert Holfort MacDowall Bosanquet (b.1841-d.1912) was a mathematician and Fellow of St. John's College, Oxford where he was a Professor of Acoustics. He was a distinguished scientist and researcher on the scientific side of music and its interpretation and effects; his ideas were published in a book . In 1876 he suggested to the Musical Association to use coloured musical scores for orchestras for different families of instruments or tone quality. His suggestions were based on the psychology of perception, and associations between colour and sound and emotions they invoke which he carried through to practical experiments. Another researcher was Prof. A. Wallace Rimington (b.1854-d.1918) who, in 1893, had a ``colour organ'' - actually a modified American parlour organ with large coloured lights in a panel above. Coloured pipe organ stops (tabs) designating the different sound ``families'' were proposed by Robert Hope-Jones and others and became firmly established in the cinema and theatre organs of the 1920s for rapid identification of the required tonal qualities.
The Enharmonic Harmonium of Bosanquet was another experiment , which now resides in the Science Museum at Wroughton after being donated by Bosanquet (accession no. 1876-473). It was built in 1872-3 and has 53 differently pitched notes per octave with 84 keys arranged in 7 rows of levers. This is known as the ``generalised keyboard'' . This design is based on ``transpositional invariance'' which means that the same fingering is used in different modes. Each row of keys is connected to quadrants and trackers to operate pallets in the reed pan. The harmonium was actually built by T.A. Jennings of Hackney Road, London. It is possible that the idea for the instrument was suggested by Herman von Helmholtz (1821-94) who was closely involved in the understanding of tone, tonality, acoustics and musical sound in general. His own instrument is described in his famous bookOn the Sensations of Tone . Ord-Hume  says he was associated with Bosanquet in building this enharmonic harmonium. The following photographs are © the Science and Society Picture Library.
Phil Fluke of Saltaire is carrying out (has now compled) a careful and detailed restoration keeping as much as possible of the original organ, which unfortunately had been stored in poor conditions for a long time. The keyboard mechanism is extremely complicated and this experiment, even if proven successful, would not easily have found its way into large scale production. Despite this there were a number of instruments based on the generalised keyboard design .
The following photographs are © the Fluke Collection and show the instrument dismantled in 2003. By 2005 it was in the process of being re-assembled.
George Bernard Shaw, in a note to McClure (see below), notes that he once heard Bosanquet play his 53 note reed organ and suggested that he was probably the only person capable of playing it at that time.
Colin Brown (b.1818-d.1896) was Ewing Lecturer in Music at Anderson's College of Music in Glasgow. His Voice Harmonium, apparently designed by Henry Ware Poole of Danvers, Massachussetts, USA, had 36 notes per octave and a special keyboard with a duo-denary arrangement. Joseph Alley of Newburyport, Massachussets built another one and Alley and Poole held US joint patent 6,565 in 1849 .
Brown continued to exhibit such harmoniums, such as on entry 3,519 in the London Exhibition 1885 where he was awared a bronze medal for design of keyboard and voice harmonium.
Poole held US patent 75,753 in 1868 for the keyboard . This was called the ``natural keyboard'' and a harmonium with one was built in 1875. This was a musical instrument which had additional keys to allow a range of scales to be played in perfect intonation instead of the (slightly inaccurate) scale of equal temperament, which is the best that can be done with an ordinary keyboard. It had more than 40 notes per octave.
A picture of the Voice Harmonium with this keyboard appears in the Science and Society Picture Library collection number SOUC100029. [who was this one made by?]
Documents are held in the Royal Institution of Great Britain archives
Teddington 1 1/4 pages, typescript. Comments on Colin Brown's Voice Harmonium, a 19th century keyboard designed to make the organ play in tune. The Science Museum plans to exhibit this properly after the war. Wrote to tell Brown's daughter this and by return received news of her death. This explains reference in the enclosed letter to the Philosophical Magazine. Is enclosing copy of reply from [E.E.B.] Mackintosh, Director of the Science Museum. With enclosures:
1. E.E.B. Mackintosh, Science Museum, to [L.S.] Lloyd, 19 March , 1/4 page, typescript. Acknowledges letter about the Voice Harmonium. Agrees with Lloyd's suggested letter to the Philosophical Magazine. Ref:W.L. BRAGG/55C/4;
2. L.S. Lloyd to the Editors, Philosophical Magazine, 21 March 1942; 1/2 page, typescript with MS amendments. Comments on Colin Brown's Voice Harmonium, which is to be exhibited again at the Science Museum after the war. Ref:W.L. BRAGG/55C/5.
The following photograph is © the Fluke Collection.
Harry Partch (b.1901-d.1974) was an American composer who used micro-tones in his work and investigated instruments tuned to just intonation and with alternative keyboards. He wrote a book on the subject  and visited England in 1935 to see and play some of the instruments here, including those of Bosanquet, Brown and the pipe organ of General Perronet Thompson. He noted that Bosanquet's keyboard was the most practical for 53 note intonation. He notes that Brown's keyboard has few familiar aspects but he found it was easy to play and its intervals and triads [are] a delight to the ear. He also mentioned that three instruments had been built.
What was left of one instrument was nearly lost as a flea market owner sold it to a joiner to take off the rosewood veneer. Fortunately Phil Fluke saw it and was able to bargain to keep the action intact. It is now (was) in the Saltaire Museum and may eventually be restored. There is another in the Science Museum in South Kensington (probably the one in the picture) and also one in Tacoma, Washington, USA.
Jennings of 127 Pentonville Road, North London created a harmonium of 4 1/2 octaves with micro-tone scaling between 24 and 84 tones per octave. The most famous of these was built for R.H.M. Bosanquet, see above. Jennings was an organ builder, born in Hereford in 1827, and also had addresses at 75 Red Lion Street, Holborn and 14 Weymouth Terrace and 199 Hackney Road.
Jordan designed a transposing harmonium which was made by J. Baynton, see Chapter 20.
Karl Goldbach sent me some more information about Jordan's transposing harmonium . He also noted that Google books hints on an article in English Mechanic and World of Science 29 (2/3-5/9/1879) p2 about a new transposing apparatus for harmoniums and American organs.
Arthur McClure, of University of Edinburgh, designed or built several instruments; piano, reed organ and a chamber pipe organ (latter by Harrison and Harrison) with 19 notes per octave. He was actually a doctor of medicine and eventually practiced at Wellington, Salop. He was convinced of the importance of using so called ``flat'' scales for the playing of early music. He also explained that some people cannot bear equal temperament on an old un-voiced harmonium, because the fierce upper partials make the false concords so evidently out of tune; and for similar reasons Wheatstone did not equally temper their English concertina until 1860. The 19 note Extended Mean Tone scale allowed notes to be closer to their true harmonic and less ``sharp'' than in equal temperament, despite the fact that the latter provided a more melodic experience to latter day ears.
An enharmonic harmonium by McClure was donated to the Fluke collection around 1989. It was built as a prototype from a one row Carpenter organ. McClure had it modified by a local piano repairer who simplified the case and added the extra mechanism to be able to operate an additional seven reeds per octave. The 19 note octave was known as Extended Mean Tone .
The reed organ has a standard 61 note FFF-f'' keyboard, but sliding bars underneath to alter the pitch. Pulling out the lever closes air from the front reeds and allow air to the rear ones. The tuning is as follows:
Front: C, C sharp, D, E flat, E, F, F sharp, G, G sharp, A, B flat, B,
Rear: D flat, D sharp, E sharp, G flat, A flat, A sharp and C flat
This meant that many true modes could be played rather than the equal temperament to which we are now accustomed.
McClure published several articles on his invention, notably in Musical Opinion. These resulted in a letter from George Bernard Shaw of 5/3/1947, also in the Fluke collection, complementing him on bringing enharmonic tuning back onto the agenda.
Dr. McClure died in around Jan'1951, shortly before publication of his article in The Organ . It seems he had become slightly dissapointed with the reception of his instruments, but still strongly believed they were appropriate for early music with harmonies played on instruments with a steady pitch.
The following photograph is © the Fluke Collection.
Moores built and sold the Harmonical, an enharmonic organ invented by Alexander J. Ellis, and they exhibited it at the 1885 Inventors' Exhibition in London. J.H. and H.K. Moore had premises at 104-5 Bishopsgate Street, London in 1880 to 1911 and a factory at 28 Scrutton Street, London, see Chapter 21.
The Harmonical had one set of reeds spanning five octaves with special tuning. Any such harmonium bought from Moore and Moore c.1885 costing £165 could be tuned this way. The precise tuning was explained by Ellis .
H. Keatley Moore Mus.B. also invented an Indian scale harmonium with 23 notes per octave. According to Partch , one of these was ordered by K.B. Deval (Honarary Secretary of the Philharmonic Society of Western India) who published his theories on the Hindu musical scale and 22 srutis. In addition to the usual keyboard it had eleven brass pegs giving the 22 srutis plus an extra key. With this, five tonalities could be played. Given the resurgence of ``chant guides'' sold in India, I don't know why this wasn't a bigger success, but apparently harmoniums were banned from Indian classical music for 30 years.
In India, Dr. Vidyadhar Oke has developed the modern 22 shruti harmonium, which can play 22 micro-tones in an octave 5 See http://www.22shruti.com. He explains the principle on YouTube https://www.youtube.com/watch?v=2QuK6cJon8w. The fundamental tone (shadja) and the fifth (pancham) are fixed, but the other ten notes are variable. The highest and lowest micro-tone for each note is a fixed point known as a shruti and on the classical Indian instruments players can vary the pitch in-between. On the harmonium, the higher is selected by pulling out a knob below the key. In this way, the 22 shruti harmonium can be approximately tuned for any particular raga (key) by simply pulling out knobs wherever a higher shruti is required 6. See .
Robert Snell (b.1802-d.1871-81) of Ball's Pond Road, London exhibited a bi-chromatic seraphine called the Chordoelian at the London Great Exhibition of 1851 in the Crystal Palace. This instrument had 24 notes per octave. It used a standard keyboard, but was controlled by around 12 pedals, one of which could be used to correct the scale for each key required.
Apparently he was known in 1825 as Robert Snell Junior, so his father, also Robert, was probably in the organ building profession. Other members of the Snell family were in business producing harmoniums around the same time and later. For the rest of the story of the Snell family see Chapters 3 and 21.59.
The enharmonic seraphine was exhibit no.528 in Class X of the Crystal Palace exhibition . The entry reads: Seraphine, with bi-chromatic or double scale of notes, producing perfect harmony in every key, without the aid of temperament; the improvement effected by an octave of pedals, one being put down, corrects the scale for the key required.
The following information was sent to me by Karl Goldbach in Jan'2008. Wilfrid Perrett (b.1873-d.1/10/1946), lecturer in German at the University of London, constructed an enharmonic harmonium called ``Olympion'' with 19 tones per octave .
We know that Wilfrid Perrett, son of Samuel Perrett and Sarah Bussell, was born in Bridgwater in 1873, the youngest of ten children. He married Hedwig Eleonora Matthiesen in Bridgwater in 1908. At the time of the 1911 census they were living at 544 Erskine Hill, Hendon and he was working as a Reader in German at the University of London. In addition to his critical work on etymology, he undertook a translation of Einstein's work from German and wrote The Heritage of Greece in Music - his interest in the latter subject led to him build an enharmonic harmonium, the Olympion. Unfortunately there is no mention of this in his book . For more of Wilfrid Perrett's life story see http://p-rr-tt.org.uk/wordpress/?p=20.
However it is noted by Gilmore, that Harry Partch had read Perrett's book and played the Olympion . He also visited the South Kensington Museum in London and there played Perronet Thompson's just tone organ. Also involved in the visit were Ernest Clements, an authority on Indian music, and Kathleen Schlesinger, a musicologist and Greek scholar. Partch received a grant from the Carnegie Foundation in 1934 which enabled him to travel to Europe and then to write his first fully micro-tonal work for orchestra. He also built a just tone harmonium which he named Ptolemy, perhaps in reference to Perrett's earlier work. Other instruments by Partch are described in Wikipedia: https://en.wikipedia.org/wiki/List_of_instruments_by_Harry_Partch. There is even a picture of a re-tuned American reed organ on stage. He can be seen demonstrating a 43-note per octave reed organ called the Chromelodeon on this YouTube video https://www.youtube.com/watch?v=P8NIpPhXpfQ.