The Electronic Organ Collection
Compton Melotone - circa 1955
This 'portable' pipeless organ
uses 12 rotating electrostatic generators, each with 8 octaves of
'fundamental' sine wave engraved upon them (the 'C' having 9
octaves), giving a generated tone pitch for each note through the
range from the bottom note of the 16' to the top note of the 2'.
Additional 'harmonics' are engraved onto the discs, to allow for
further tone synthesis.
The tone is produced by a
generator having a sine wave engraved upon a rotating disc, which is
in close proximity to a static disc, similarly engraved. An HT
voltage is applied to the circuit, and the varying capacitance
produced by the rotating disc against the fixed disc produces an
oscillation, the pitch of which equals the sine wave engraving.
The
12 'note' generators are identical, and are interconnected to the
drive motor by a long belt which passes over pulleys on the ends of
the generator shafts. These pulleys vary in size, thus rotating each
generator at a slightly different speed, in order to produce the
notes of the scale. The Vibrato motor has an elliptical pulley
attached to its shaft, and introduces a 'wow' onto the drive belt,
thus producing frequency modulation.
The stop tabs select the
harmonics and pitches which are to have voltages applied to them by
the keys, and many interesting tonalities can be produced by this
synthesis method. All very similar to the Hammond generator and
drawbar principle.
Attack and decay characteristics
are simple to apply for each stop, as there is a resistor /
capacitor network for each note's HT input. A sustaining
'Vibraphone' was a standard stop on these instruments, and as the
sustain capacitors aged, sustain lengths of up to 3 seconds could
become achievable.
There are no 'key clicks' or
other unwanted keying noises, due to the fact that all tone
switching is carried out PRIOR to the note generator, unlike the
Hammond Organs, which switched the Audio Outputs of their
generators, thereby producing the infamous and undesirable (except
to jazz musicians) clicking sounds as each key is pressed.
The design of the Compton
Melotone originated in the electrostatic attachments which John
Compton developed in the late 1920's for his Theatre Pipe Organs,
where small pipe instruments with perhaps only 5 or 6 ranks of pipes
would have a 'Melotone' attachment to increase their tonal
flexibility, the only variation, being that these early melotone
units employed two rotating discs, and each note or harmonic was
individually engraved onto them.
The Generators, HT Power Supply,
and Valve Amplifiers, are all accommodated within the console. The
Loudspeaker Cabinet is a separate unit.
Larger instruments than the one
pictured, were the 'Electrone' and the 'Theatrone', and these
employed the same principal of 12 generators, but with multiple
harmonics for each note, each individually engraved onto the discs,
resulting in much larger tone generators, which as a result, had to
be placed in separate cabinets. The note inputs to the generators
were switched by relays similar to the ones found in Compton's pipe
organs.
The Compton Melotone was donated
to NITOS by David England and David Pattinson of Newcastle, who had
commenced the restoration of the instrument.
Solina EMINENT F227 Electronic
Theatre Organ
In the early 1970's, Solina / Eminent of
Holland virtually invented the chorused String Ensemble sound which is now
found on almost every electronic / digital keyboard instrument. They
marketed slightly differing ranges of organs under the 'Eminent' and 'Solina'
banners.
The Eminent organ in Britain has long
been synonymous with virtuoso performer John Mann, who has been touring with
his Eminent 2000 Grand Theatre Deluxe and matching Solina tone cabinet for
many years now, both with his 'One Mann Show', and his 'Electronic Organ
Spectaculars'.
Unlike other instruments in this class,
the pedalboard is fully polyphonic ie more than one note may be played
simultaneously.
Fitted with a synthesised 'rotary
tremolo' effect, and both electronic chorus and celeste, this organ with
both its 'drawbar' type controls, and preset sounds, of both orchestral and
percussive tonalities, ensures that a very wide range of full sounding tones
can be made by this instrument.
GULBRANSEN President Electronic theatre
organ
complete with factory customised pedalboard of 30 notes.
The Gulbransen range was one of the first
'analogue' electronic organs to create a realistic piano sound, and it is
for this, as well as their special multi-channel internal Leslie rotary
loudspeakers, that they are most famous.
A remarkable sound for a completely
analogue instrument, all tones are synthesised from the basic 'tibia'
waveform, and it is fitted with both stop tabs and Hammond style drawbars.
This instrument was donated by Mrs C
Campbell of Dunbar.
The one time 'flagship' of the Hammond
range, the 1973 HAMMOND X66 was built in the period of 1969 to 1975.
The X66 was the first of the transistor based organs from Hammond.
Unlike earlier Hammond organs which used
a 'tone wheel' for each note, it uses a set of 12 tone wheels which simply
generate the top 12 notes, from which all other noted are divided from by
standard transistor dividers.
In addition to the sine wave tones
generated by the tone wheels, an additional set of transistor generated
sounds are made available on stop tab, to make this instrument sound more
'theatrical'.
An interesting feature, is an automatic 'arpeggiator',
consisting of a set of rollers in the keyslip of the upper manual, which,
when stops are allocated to it, allows the player to introduce a 'harp' like
arpeggio effect with suitable sounds, the arpeggio playing whatever notes
are held down on the lower manual at the time of operating the roller
switches.
Various percussion sounds are available
on the upper manual, including Marimba, Glockenspiel, Chimes, Piano, etc.,
as well as an early 'cymbal' sound, which is a very basic 'white noise'
generator, triggered by a key or pedal operation.
This instrument was donated by David
Mackay of Hawick.
The 'WURLITZER' 4525 has two full manuals
and a 25 note pedalboard, in a traditional 'horseshoe' console, complete
with stop tabs and stop rail illumination. Magnetic reed switches are
used for the pedal contacts, 'neon' dividers are used for the monophonic
pedal tones (only one note may be played at a time) and it utilises 'pot
coils' for tuning the 12 master oscillators. Otherwise it is a fully
transistorised instrument.
The rotary 'Spectra Tone' loudspeaker
system is incorporated into the instrument. The Spectra Tone system differed
from the 'Leslie' system, in that the loudspeaker itself was mounted on a
rotating arm.
This instrument was donated by Miss
Debbie Curtiss of Cannock, Wolverhampton, in memory of her late father.
A LESLIE 125 loudspeaker was included in
the donation, as well an 'ACETONE' Rhthym Unit, which was the top of the
range unit in its day.