So, how does the device work? The operating principles, inspired by mechanical stringed instruments of yesteryear, are not complicated.

Unlike its orchestral counterpart, the Solo Cello uses a single, metal string. This is anchored at the right-hand side of the unit, passing over the equivalent of a bridge, between the poles of an electromagnetic pickup, above a row of 37 stopping fingers, to the ‘neck’, where it is wound around a motorised tuning capstan at the left-hand side. A resined bowing wheel is in constant motion, driven through a gearing system by an electric motor. This, together with the appropriate stopping finger, is moved into contact with the string, whenever a key is depressed. The drive motor also operates a cam device, which affects the tension of the cello string, thus producing a degree of vibrato.

The signal from the electromagnetic pickup is fed to an amplifier, which outputs to a horn speaker.

Unlike the Melotone, the volume of the Solo Cello is not controlled from a swell pedal. The horn speaker is situated in the Solo chamber of the organ, behind the swell shutters, and stopkeys at the console, provide three (sometimes four) preset volume levels.

Thus, a typical stopkey layout would read:

Solo Cello
1
2
3
4
Amplifier

It is essentially a melodic device, over 37 notes – if the organist plays a chord, only the highest note will sound – and is available on the Solo division of the organ. For each key depressed, the appropriate relay operates on the unit, causing the aforementioned stopping and bowing of the string – in the same way that a player would stop the strings of his instrument, to produce a note of the correct pitch.

Two thumb pistons (marked Sharp and Flat) are provided at the console. These control the reversible motor of the tuning mechanism, providing the organist with at least some hope of keeping the Solo Cello in tune with the rest of the organ!

There is an additional need to maintain a supply of resin for the bow. The first units used resin powder, which entailed keeping the hopper replenished, while later units used resin sticks. This task often fell to the Chief Operator!

Sufficient to say, difficulty in keeping this device in tune, coupled with its generally unmusical sound, led to a rapid decline in popularity among organists and audiences alike.

The above photographs should help you to spot the various parts of a Solo Cello unit, mentioned in this text. The first of the black and white photographs (courtesy of John D Sharp) shows unit Number 10: Carlton, Norwich. The colour photograph (courtesy of Ted Crampton) of the same unit, affords more detail of the tuning mechanism, while the third photograph shows, in close-up, the string and stopping fingers of unit Number 14: Dreamland, Margate.