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MMD > Archives > February 2003 > 2003.02.25 > 12Prev  Next

The Leach & Overington 89-Key Concert Organ
By Andrew Leach

An 89-key mechanical organ designed, built and owned
  by Dr. Andrew Leach and Mr. Tony Overington.

What started out as a fairly casual idea back in 1980 soon began
to grow into a huge project.  It was some months later, after the
introduction to the idea, that we were enjoying one too many pints of
Sussex ale in a local hostelry and were discussing the idea further.
One of us said, "We won't just build a toy organ -- we'll build a
proper one."

"Right," said the other, "proper it will be!"

And so began in earnest the plans for this mighty instrument.  Well,
it seemed possible with our combined experiences of joinery and organ

We decided we would not be copying another maker's organ but, rather,
it would be to our own ideas and design.  It had to be, first and
foremost, musical and able to play a wide range of music -- not just
a fair organ or a street organ or a dance organ, but a concert organ.

Many traditional ideas of mechanical organ building have been used
in its construction, but also a lot of original ideas are used, often
using more durable and efficient materials than would have been used
80 years ago.

The musical scale or arrangement of notes, upon which it is based
required some considerable thought initially, but it was eventually
decided that, of all the mechanical organs ever built, Mortier of
Antwerp had probably developed the most musically successful scale,
And so we based the organ on the 92-key Mortier scale which is fully
chromatic in all four musical departments.  This also meant that we
could obtain music fairly readily for it, with only minor alterations
needed to the scale layout.

It was at about this stage that we met the late Peter Watts of Chipping
Norton, who owned a 91-key Mortier organ, and the late Steve Clarke who
worked for him arranging music.  A friendship grew up and over the
years these two gentlemen gave us much help in designing the organ.
It was Steve Clarke who taught us much to do with specification and
pipe scaling.  He arranged most of the music so far for the organ.

We spent the first two years experimenting with ideas and mechanisms
in the workshop trying to get the right methods of doing things and
also the right sounds from several test pipes.  It was often quite
disheartening and sometimes we would just give up for a while to return
a week later and crack it almost immediately! But gradually we learned
(the hard way usually) and so various components started to pile up.

One of the most difficult tasks was to successfully make and voice
violin pipes.  We had already decided that there were to be a
substantial number of ranks of violins in order to create a rich sound
on the melody section, but it was an almost impossible task for some
considerable time to get this enormous section of pipe work correct.
It all suddenly fell into place one day and thereafter we were kept
very busy voicing and finishing several hundred violin pipes for quite
a few weeks.  From then on we were kept very busy building more and
more pipes and wind chests.

Both our houses, workshops and garages were filling up with piles of
components and both our wives were beginning to wonder when it would
all end!  After many interruptions for more pressing things in life,
a few years later the time had come to partially and temporarily put
the various components together to see if it worked.

At this stage we had to build the main wind chest.  This is a
considerably sized lump that sits in the middle of the instrument
and weighs probably 300 kg or more.  It is 8 feet long, 3 feet wide and
1 foot deep.  It is in effect a giant relay and distribution box and is
crucial for the correct functioning of the entire organ.  On an organ
of this size we decided to be generous in its design with large main
pallets and plenty of windway space.  Eventually enough space was found
in one of the workshops to build a temporary frame and erect some of
the chests and pipes.

It was to be at least a couple of years more before we had any music
from it though, for the project had grown in size considerably from
the first ideas and we had to purchase two specially made centrifugal
blowers to power it.  One of these is a 3 hp motor providing wind at
10" water glass pressure at 450 cubic feet per minute, and the second
takes 100 cubic feet of this to boost the wind to 20" water glass (wg)
pressure with a 1 hp motor.

This latter blower is used to power the harmonic tubas.  These pipes
were rescued in 1968 from the demolished Odeon cinema at Chadwell Heath
in London and had been stored all these years for just such a project!
They were made by Compton.  Finally we had some music from the beast.
From then on we had many more pipes to make including some extraordinarily
difficult carillon flutes; the smallest of these has a speaking length
of just 3/4".

We also acquired an octave of 16-foot stopped Bourdon made by Wurlitzer;
these came originally from the Empress ballroom in Blackpool.  They are
heavily constructed with thick arched lips and are finely made.  To
help balance these we had to build a rank of 8-foot open pipes of very
large scale.  The low A of this rank has a scale of 5-3/16", a cut-up
of 2-7/8" and is made of 3/4" thick timber.

These and their chests and also the 8-foot stopped pipes and chests are
all made from tulip wood.  The pile of timber just for this section
half filled one of the workshops.

The counter melody cello grave is of unusually large scale too, with
the low C of this rank being about 87" long, and having a scale of
3-5/16", a cut up of 1-1/8" and is made of 7/16" thick timber.

The time came to look for a suitable vehicle into which we could
build the organ, a task which seemed daunting at first.  We did
consider building it onto a separate trailer but the practicalities
of maneuvering such a vehicle ruled this out, and so it was fortunate
that very soon a large Bedford TK with a Luton style body was advertised
locally.  It was ideal and soon purchased.

The lorry had seen better days and so the decision was made to
completely overhaul the entire vehicle, which included removing the
old box body, stripping down the whole vehicle to the chassis and
rebuilding the mechanics and cab and having a new purpose-built body
fitted back onto the chassis.  A 9 kVA generator is fitted underneath,
big enough to power the organ.  This all in one vehicle, which means it
is relatively easy to move around.  Even so, the organ fills almost the
entire lorry.

When finished the main frame and case of the organ was constructed,
a substantial construction which is bolted to the main chassis.  From
then on all the many parts were fitted in, and something like three
miles of various sized tubes were run in.  At last we were able to hear
the organ as it would eventually sound.

The decorative front of the organ is based on architectural lines of
the Georgian period.  The purists, however, will point out that the
lower dental mouldings (which were in fact the moulded ends of the
ceiling joists) are missing, this for a very good reason.

When the full size drawing for the top were completed it became very
obvious that the fluted columns and mouldings and lower wainscotings
had to be in the same proportions.  This would have denied access to
the front of the organ when the front was closed and added considerable
more weight to the vehicle.

It was therefore decided to leave out the lower dental mouldings
and scale the lower front down, thus allowing access.  One point of
interest: the top moulding is machined from solid 11-inch by 2-inch
thick timber.  It took 45 minutes to set up the machine, and 6-1/2
minutes to machine the final job.  The guilding on the organ front
is 22-carat gold leaf.

All the pipes stand on their own off-wind chests, 42 chests in total.
Violin Piano is on 2 chests, and Violin Forte is on 3 chests.  This
was done to facilitate tuning but also it means that each rank receives
its optimum wind supply.

The melody Harmonic Tuba is augmented with a rank of Open Flues an
octave lower and a rank of Violins an octave lower in order to obtain
the correct harmonic balance from this register.  (The reeds on their
own were found to be extremely harsh).  The counter melody Harmonic
Tuba is likewise augmented with a bridged Open Flue and a Stopped Flue.

Both the counter melody and bass Tuba chests are operated on an exhaust
pneumatic system, because these pipes play on the higher 20" wg
pressure and this overcomes the pressure differential problem between
10" wg action pressure and 20" wg pipe pressure.  The melody Harmonic
Tuba, although also on 20" wg pressure, has smaller pallets and hence
a conventional push rod system is used.

The 16-foot stopped Bourdon and 8-foot Open Principal are also operated
on an exhaust pneumatic system due to the very large pallets in these
chests.  The percussion has its own secondary relay system to allow
the motors to work as fast as possible.  There are two single rise
reservoirs, one supplying 10" wg pressure to the main organ and one
supplying 20" wg pressure to the Tubas.  The register box is an air
lock type on 20" wg.

The longest pneumatic signal from key frame to main chest and back to
the pouch on the off chest is nearly 40 feet and there is no discernible
delay in the speech of this pipe, the lowest A on the 16-foot Bourdon.

Various types of timber are used, a lot of the pipes being made from
Siberian archangel pine, with the fronts from Douglas fir.  Some pipes
have been made from reclaimed old church organ pipe timber, over 100
years old, which is extremely dry and ideal for this purpose.  The
large 8-foot open Principal, the 8-foot stopped Bourdon, and their
chests and the counter melody and bass Tuba chests, are all made from
tulip wood.

Many of the soundboards and off-wind chests are made from sycamore
and some from beech.  Only the best quality leathers have been used
throughout the organ, with no 'seconds' used.  All valve push rods are
made from stainless steel running in Delron bushes and will probably
last forever.

The key frame has 89 keys, 88 of which are used to control all functions,
with one spare key.  All the electrical controls are positioned above
the key frame for ease of use.  All the pipe work in the centre case is
operated from ventils incorporated in the main wind chest and the side
case chests are operated from individual ventils by their respective

The four big Tuba chests are operated by large exhaust pneumatic
ventils which supply wind extremely quickly to these high pressure
pipes.  Relays are used to operate the primary valves to these ventils.
It is only by adhering to these principles of separate off-wind chests,
pneumatic relays and carefully calculated pallet sizes, that the organ
plays so promptly and accurately.

It is thought to be the largest mechanical organ ever built in the
UK entirely from scratch.  It is a project that has stretched our
imagination, our energy, our determination, our finances and our
patience to the limit, and without the patience of our wives it would
never have succeeded.  We think we have however succeeded in proving
that such a thing can be done by amateurs.

A new professionally recorded CD of the Leach & Overington 89-key
Concert Organ, Volume 2, is now available, featuring music arranged
mainly by Jan Kees de Ruijter and Tom Meijer.  Titles on the CD
include:  Buglers Holiday; Scott Joplin selection; New York, New
York; Stomping at the Savoy; Crazy Party Mix; No Matter What; Pink
Panther; Rhapsody in Blue; Mortier Boogie; Memories from Cats; The
Caliph of Baghdad; Toselli Serenade; Second Waltz; West Side Story.

The new CD is available from me at

  Leach & Overington,
  4 Daniels Cottages, Newpound, Wisborough Green,
  West Sussex RH14 0AX  England.

Price is 10.00 UKP plus 1.50 p&p (UK mainland).  Overseas postage
will be more and will have to be determined at time of request,
depending on country.  Cheques made payable to Leach & Overington
in UK pounds Sterling, please.

Andrew Leach

 [ I will place the photos and specifications and scale details
 [ at MMD Tech site,  -- Robbie

(Message sent Sun 23 Feb 2003, 21:02:56 GMT, from time zone GMT.)

Key Words in Subject:  89-Key, Concert, Leach, Organ, Overington

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