Two Organs in St John's

Stephen Doughty, Director of Music and Organist at St John's, writes about the second organ installed to perform Vierne's Messe Solonnelle during the Edinburgh Festival:

On the 28 August this year, following a month of varied and exciting music-making covering some four centuries which included no less than two world premieres, the grand finale of the Choir of St John's Festival Worship took place. In a music list that had featured music for triple choir and a chamber orchestra this finale was notable, firstly for placing the choir in the acoustically-excellent gallery, and for showing off our latest acquisition- a new digital organ built by the assistant organist in St John's, Peter Horsfall.

Historically having more than one organ is a precedent that has been well established. A quick tour around some of Europe’s more significant cathedrals and churches reveals the Grande Orgue sitting in a commanding position in a gallery above the West door (the best position, incidentally) with a smaller Orgue de Choeur above the altar at the front of the church, close to the singers. The architecture and music of such buildings in this country generally doesn't support such musical excitement/potential sadly- the main organ is almost always at the front of the church above the choir stalls which are typically placed left and right in the Choir.

The practice of playing two organs alternately was a performance method already well entrenched even as early as the fifteenth century- an organ "duello" between Claudio Merulo and none other than Andrea Gabrieli was one of the more combustible examples in history. When I decided to programme Vierne’s monumental Messe Solonnelle, written in 1898 to be performed in Paris' Church of Saint Sulpice with its magnificent organ, (the instrument itself is a candidate to become a UNESCO World Heritage Site!) Peter jumped at the challenge of building a second instrument to show off the work’s full potential.

Typically the smaller orgue de choeur plays along with the choir, doubling their vocal lines and adding softer instrumental interludes while the brooding grand orgue powers out big chords and ground shaking introductions, often marked fff which in French organ terms is very loud and snarly indeed- great stuff! However I can’t help wondering how well the two instruments- which in a cathedral such as Notre Dame are a significant distance apart- played together. Was there an 'intermediary' conductor half way down the church..?! In the case of St. John’s technology again leant a hand with a TV camera and loudspeaker so the gallery organ could be heard at the front of the church- very successfully in my opinion!

Stephen Doughty, www.stephendoughty.co.uk

Pete Horsfall at the Gallery Organ which he built for St John's Church: the main organ is in the Choir.

Engineer Pete Horsfall, Assistant Organist at St John's, describes how he built the new gallery organ:

The gallery organ is an electronic instrument, comprising a mixture of new, old and refurbished elements. The design and construction involved mechanical, electronic and acoustic considerations – much as a 'real' pipe organ does.

On the mechanical side, the main components are two keyboards and a pedal-board. The two keyboards have been built up from items that were replaced in the Church's main organ during its refurbishment some years ago. Due to their age and the interim storage conditions, the majority of the keys had become prone to sticking and the electrical contacts were unreliable until each key was systematically adjusted and cleaned up. The weight and the geometry of the moving parts of a traditional organ keyboard is greatly superior to a typical synthesiser keyboard, so the refurbishment of these keyboards seemed the most appropriate option for this project. The pedal-board has been borrowed from another instrument and presented no particular challenges – other than the fact that the pedal-board is wider than two 'table legs' that it sits between! The bench seat is also borrowed from another instrument.

The lesser, but still crucial, aspects of the mechanical construction involve a customised table-top that the keyboards sit on, the music rest, and also supporting brackets for the loudspeakers. The table-top enables the keyboards to rest on a conveniently-positioned pew; luckily, the pew lent itself to the instrument’s proportions being fairly close to 'standard' dimensions, although it is doubtful that any alternative plan would have been devised even if that had not been the case. The need for a music rest epitomised many aspects of the project as a whole, in that even the apparently simplest components require to be built up from nothing, and can be every bit as challenging as the 'major' tasks - it may or may not be apparent to readers that anything requiring non-right-angled wood cutting is likely to give some headaches.

On the electronic side, each keyboard and pedal-board is fitted with a stand-alone circuit that generates a 'MIDI' signal output. (MIDI is a standard protocol used by modern synthesisers to link between electronic instruments.) The MIDI circuits connect to each individual key note (61 on each keyboard, 32 on the pedal-board), and generate a coded data stream for every 'event' (ie. key press, or key release). These circuits conveniently rationalise the amount of external wiring required, in much the same way as a computer keyboard connects to a PC using only 4 wires, despite the keyboard having 80 or so different keys.

The MIDI signals from each keyboard/pedal-board are merged together in another circuit – a non-trivial operation that interleaves the data streams from the different sources, each of which has no knowledge of any data that might be emitted from another source concurrently. In addition to the key-press information already described, the organ needs to accommodate control of the 'registration' – this is the term used to describe the different instruments (or 'stops') that are active at any time. The keyboards were already equipped with 'thumb piston' buttons, positioned just below each keyboard to allow pre-programmed stop combinations to be recalled at the push of such a button. These buttons, together with a separate panel that houses 6 additional piston buttons, have each been configured to generate selectable MIDI messages, which are merged with the keyboard streams to allow full control of the sound-generating synthesisers.

With regard to the acoustic and sound-generating aspects, it is likely that the quality of the synthesisers and the complementary acoustics of the building are of similar-ranking importance. The synthesisers, which generate the pipe organ sounds, are commercially-built devices that are designed to be used either as stand-alone instruments, or integrated into traditional pipe instruments. They are probably as good as any synthesised pipe instrument can be. But – as is often asked about synthesised organs – just how 'good' is that?

The synthesised sounds are based upon high fidelity recordings of real organ pipes (this is known as 'sampling'); mathematical functions are used to precisely extrapolate the recorded samples across all different key pitches. Whilst this, in theory, gives a truly authentic replication of the original sound, such accurate techniques can actually be the downfall of synthesised instruments – the sound is 'too good' or 'too regular' to be convincing. The organ synthesisers must therefore apply a controlled amount of instability and irregularity to the sounds in order to create a realistic effect. Working in conjunction with a high quality amplifier and loudspeaker system, and with the Church's natural acoustics also colouring the amplified sound, the common opinion seems to be that our gallery organ does create a pleasing and convincing sound. It is interesting to note that, soon after the instrument first sounded at St John’s, some previous concerns about "will it have enough 'body' to it?" gave way to questions about "will it sound French enough?" – immediately raising the bar of expectations to optimally match the requirements of the Vierne Mass that had been the trigger for constructing the instrument!

The instrument was constructed over the course of 4 months, and completed in July. As far as possible, the various different circuits were tested – and the bugs eliminated – before the organ was assembled in the gallery. A number of hardware and software modifications have been made to the electronics since that time, to implement a few unforeseen requirements and in response to the most persistent of the bugs that were encountered - namely, phantom notes sounding on their own accord. The 'phantom notes' bug entirely vindicated the decision to include a 'panic button' into the design, though this bug now appears to be resolved, and the 'panic button' has not been used for a while now.

Whilst the aim has been to create a traditional-style instrument, the electronic implementation does open up other possibilities that could easily be incorporated (a 'Hammond' electronic organ sound, for example?!) One might also, perhaps, devise some alternate functions for the 'panic button' – any suggestions will be received with interest!