Alan Edward Williams

Composer/ cyfansoddwr

Playing the Echo: a musical-acoustic collaboration

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Every so often a project comes along which is so attractive that I want to drop everything to make it happen. Playing the Echo, part of the Manchester Science Festival, was one of these and proved to be an excellent example of what happens when science and the arts collaborate.
My colleague Trevor Cox, Professor of Acoustics at the University of Salford, had been asked to give a talk in the Manchester Science Festival about the extraordinary acoustic of Manchester Central Library Reading Room. cwbmb4lweae-xb4-jpg-smallAs Trevor is also a musician (a rather fine saxophonist on the quiet) and we’d been talking about doing something together for a while, he asked me if I’d do something musical for the event.
I didn’t need asking twice. If you’ve ever been in the reading room, and in particular, if you ever went in before its recent renovation (2008-12), you’ll remember the surreal acoustic effects created by any audible movement such as (typically) a pencil dropping, a cough or a sneeze. As a schoolboy and later as a student I would sometimes some and use the library, nearly always in the old Henry Watson then tucked away on the third floor, but I would always find some excuse to go into the reading room, and unobtrusively drop something or cough extravagantly, just to hear the echo.
At that time, before acoustic treatment as part of the refurbishment, there were two really notable features – one was the extensive reverb, which Trevor tells me was formally around 3 seconds. The other, more obvious, was the repeated echo, most obvious at higher frequencies – which is why pencil dropping was so effective. A single source could be heard up to 5 or 6 times reflected off the hard surfaces of the dome.
After acoustic treatment, both the reverb and echo were dramatically reduced, leaving only a single noticeable slapback echo around a fifth of a second after the initial source.
My research student Adam Hart (whose AHRC project is actually digital music learning interfaces in schools, but who is kind enough to tolerate my many demands on him as an all round technologist) and I went in to the reading room before it opened – Trevor had already been in with his sax, and advised us that short, sharp sounds would be more effective in the acoustic. So I asked Gravity Percussion duo to play, and it turned out they had already played once before in the room, and were able to offer some advice on the acoustic as well.
Adam and I were equipped with two pairs of claves and recording equipment. We wandered around the room for a bit, playing with the acoustic and recording it, and noted that towards the centre of the room, the slap-back echo was very clear and focused, and that towards the edge of the room it became more diffuse. OK, we thought, that’ll do. I measured the echo, worked out what metronome mark I’d need to make the echo “slot in” to the gaps between notes: this turned out to be crotchet =139 – if a crotchet is played at that speed, the echo ‘plays’ quavers in between. I reckoned that as guitarists often use digital delay in this way (such as the Edge from U2), it shouldn’t present too many problems for the ensemble even if the echo was generated by the building. I also set the tempi so that sometimes the echo would slot in as a compound time quaver – in 12/8, at crotchet = 112, the echo is the second quaver in a dotted crotchet beat.
My other main thought in writing the piece was also architectural – the room is ringed by a colonnade of 28 pillars in 4 segments, separated by doorways, and atop them is a quotation from Proverbs: 4:8 ‘Wisdom is the principal thing; therefore get wisdom: and with all thy getting get understanding.’ This gave me a title for the piece – Pillars of Wisdom.
The four entrances can be disorientating, and counting the pillars initially made me think of another ring of upright stones I’d written a piece “about” – Bryn Cader Faner,img_5895 near Talsarnau in Gwynedd. This bronze age circle is located at the junction of two ancient roadways linking important trade routes in North Wales. The two locations could hardly be more different – one on a bleak mountainside, one at the heart of a vibrant, modern city – but they are both collective expressions of the importance of culture, placed at significant junctions.
So I used the same procedures to write the piece as I did with the one about Bryn Cader Faner, Meini Hirion, which I wrote for my ensemble ACMG at Salford Univeristy. I also wanted to use the ‘keynote’ sound of the centre of Manchester –the D/A diad played by trams when they are in the city centre. As it happens, that was the keynote of Meini Hirion as well – pure co-incidence.
We knew that high frequencies weren’t as well reflected as lower frequencies in the reading room – or more accurately, the prominent high frequency reflections of the existing space had been most successfully damped by acoustic treatment. I wanted to show this in the piece, so I started it with 5 basic frequency bands moving from high to low – claves, high woodblock, low woodblock, bongos high and low. This opening passage is about establishing the tempo so that the echo slots neatly between the played strokes.
Then, in a fit of theatricality, one player walks to the perimeter of the room while the player in the middle plays a ‘holding pattern’. The perimeter player reads a series of notes which I’d blu-tacked to each pillar – and these notes are passed to the middle player, who plays chords derived from them on the marimba or vibraphone. While theses chords are being played, the perimeter player walks to the next pillar for the next chord. All 28 pillars have a separate chord, and these will work in any order.
It was important at all times that eye contact was possible between players because the acoustics of the hall made the normal listening difficult, so I initially placed the marimba and vibraphone opposite each other as close as possible to the central plinth-type thing that dominates the centre of the reading room (it used to be the librarians’ desk and hide a spiral staircase to the store underneath).
It turned out that this made it almost impossible for the musicians in the last section of the piece, where the perimeter player returns to the centre and they play various ‘hits’ in unison. We discovered that the room’s acoustic created an extremely strong focal point on the opposite side – exactly where the other instrument was placed initially – and this focal point was not only much louder than the sound leaking round the plinth but also slightly delayed. The musicians had to have sight of each other to play in sync so we had to slightly offset the instruments.
Prior to the performance, Trevor had given an introduction to the acoustics of curved spaces in a separate performance space. The audience then walked up to the reading room and were invited to wander round the space to experience the different qualities of sound created by the hall’s acoustics. In this accompanying 360 video made by Trevor and his team, half the notes you’re hearing are actually reflections from the room. The microphone was placed more or less at one of the focal points, so the hall is really acting as an amplifier to the signal.


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