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Bass Tone Bars


GENESIS OF AN EROICA
May 2013
Chris Banta

Chris Banta Marimba Eroica


Project Overview

Harry Partch - How the original Marimba Eroica began:

Back in the 1950’s, composer, Harry Partch, a philosophic music man seduced into carpentry, designed and built musical instruments to fit his special micro-tonal scales. To accommodate the lower region of the musical spectrum, Harry built a bass marimba using organ pipe resonators and large bars. He decided that the marimba’s lowest Cello C note (at 65.4Hz) was not low enough. This lead to experimentation into contra-bass frequencies powered by oversized marimba bars and huge resonators. Voila!...the Marimba Eroica was born.

 

How this project began:

John Schneider, who is the founding director of the Grammy® nominated ensemble PARTCH, approached me to discuss the possibilities of my building the Eroica. In his desire to expand the ensemble's repertoire of Harry Partch compositions, this necessitated the need to include the Marimba Eroica as well. His technical guidance, musical direction, and unwavering confidence in my bass marimba building skills, made this project possible. 

 

 

Brief Overview of this Instrument:

Weighing in at 847lbs., the resulting instrument has four pitches: A-56Hz, E-42Hz, C-33Hz, and heaven forbid, an infrasonic super low F at 22Hz! The tone of this low F is not detectable by human hearing. Instead, the ear senses the emitted frequency as pressure pulses. Evidence of its function is manifested by the rattling and buzzing of windows, loose objects hanging on walls, and other easily-disturbed things including humans. In fact, during testing one of the neighbors thought he was sensing the start of an earthquake. He walked next door to my shop and immediately recognized the cause of his disturbance.

 

This new instrument represents the existence of a second Eroica. Though, rumor has it that a 3rd Eroica has been built, by the group musikFabrik, that will be debuted in Cologne, Germany this coming September. The original Partch Eroica currently resides at Montclair State University.



Construction Timeline

 
March 2012 - Low E Bar

Rough-sawn sitka spruce cut down to size.  Finish sanding and the start of the laborious tuning process requires wood to be removed in small gradual amounts from the undercut arch with frequent checks using the strobe tuner.


Rough tuning of the bar to one-quarter step sharp of pitch.  This allows for the node points to be accurately located.  Bar will eventually be held in place with heavy duty cord.


June 2012 - Low A, C and F Bars
Continued tuning and testing of the A bar.  On the C and F bars, inspection is necessary to determine the "best side" for the playing surface.


The same routine on the C and F bars - Cutting bars to proper length, removal of the undercut arch, more tuning and testing.  Drilling mounting holes at the node points.  All four bars received their first clear coat.
 

July 2012 - Low E Resonator Box (David Canright)
Many years ago, David Canright had built a low E resonator box (at the far left) that was useful in establishing proportional internal volume sizing for the new A, E, C, and F boxes.  A very helpful visit from Danlee Mitchell and John Schneider lead to a discussion on the technical aspects of large resonators.  (Note: The protruding part of the Canright box contained a moveable stopper.  It was removed, the opening sealed, and the box was tested to evaluate the volume for the new E box.)

July 2012 - New A Resonator Box
This is the sequence of steps used to fabricate the A box.  "X" bracing is used to stiffen the walls along with a threaded rod spanning between the walls. This redundancy provides enough rigidness that the walls cannot breath or flex from the energy created by the vibrating bar.  This design drives more energy out of the resonator's opening to optimize loudness.

The opening is cut into the box.  Bar, sitting on foam, blocks is used to test resonance.  In this particular case, the resonance of the A box was a slight bit sharp of the target 56 Hz, and coincidentally, so was the bar. The resulting resonant "boom" tone was quite strong.  Another visit from John Schneider testing the low E bar on the Canright box.

Construction of the new E resonator box was very similar to the A box.

August 2012 - Low F Resonator Box
Preparing large 4 x 8 panels with "X" bracing

Lots of glue and clamping pressure is needed to force joints closed, followed by heavy duty deck screws.  Clamps remain in place for two days to ensure all glue has fully cured.

Three threaded rods are required to keep large paneled walls rigid.  A tuning collar is inserted into the resonator opening.  An audio tone burst is then sent into the opening which will cause the resonator to ring.  The ring is then read on the strobe tuner which displays the exact pitch of the resonator. The ultimate test is the placement of the bar on the resonator, then striking it with a mallet.

The size and weight of the large resonator was becoming so cumbersome that handles had to be fabricated and attached to the box. 


The A and E resonators required mobile bases to raise the bar height.  They were designed to provide a 5-degree tilt, which allows the audience to see more of the bar during a live performance.
 

October 2012 - Low C Resonator Box
By the time we get to the fourth resonator box, the construction processes have become very predictable with difficult steps anticipated in advance so proper tools and materials can be prepared.

November 2012 - Four Functional Pitches
The four resonator and bars are fully functional. It was time to discard the foam and instead, permanently mount the bars to their resonators.

December 2012 / January 2013 - Bar Mounts
Mounting blocks, made from hard maple, are designed to contain the bar in a precise acoustical alignment over the resonator opening, and will not shift regardless of how hard or often the bar is struck.


Blocks are mounted on the resonator with the mounting holes spaced to match the node points of the bar.  Long deck screws holds the mounts in place.  Bars are strung up using heavy cord and hand made felt washers.  A piece of shop wire is threaded like a needle so the cord can be pulled through all the holes.  A tension springs is used to keep the cord taught.

February 2013 - Corner Molding
Corner molding is applied to hide the end grain of the plywood panels and to give the instrument a finished look.

March 2013 - Staining and Finishing
Wood dough is used to fill all nail holes and other little blemishes. The entire resonator is sanded and wiped clean.  Two coats of a special wiping stain is applied.  Finally four coats of semi-gloss clear are applied.  The bars also receive their last coating prior to final stringing up of the bars.  John Schneider inspects and plays the final instrument!  "Looks like we have ourselves an Eroica!"



Debut Performance at REDCAT Theater, Los Angeles
June 7-8, 2013
"Partch: Eroica Dances"
PDF Icon Handout

Marimba Eroica