1 string, 2 strings, 3 strings or more

[John Delacour]

At 22:12 17/09/01 -0500, Ron Nossaman wrote:


>...Blending the monochords into the bichords is usually more a matter of 
>keeping unison tensions similar across the transition and not making 
>enormous changes in core diameters. That's scaling.

By 'unison tensions' do you mean the sum of the tensions of the strings of 
the unison?  If so, then you are saying that a bichord unison with strings 
at a tension of 180 lbs. each should be adjacent to a monochord at 360 
lbs.  That would indeed require a huge jump in core diameters and would 
take the tension of the monochord way above reasonable levels.  A typical 
(and acceptable) singles/bichord break might have the note 14 bichords at 
180 lbs. on a No. 19 core with the top monochord note 13 at 260 lbs. on a 
20.5 core.  Other factors can play a part according to the peculiarities of 
an instrument and a greater jump in core diameter is sometimes needed.

An example would be

Note 13  length 1220 mm.  o/d 3.15 mm  mass 67 gm.  tension 268 lbs
Note 14  length 1200 mm.  o/d  2.55 mm  mass 2 x 45 gm.  tension 183 lbs.


>   Blending tone across the bass / tenor break is an exercise in both 
> soundboard/scale impedance balancing, and good scaling practice.

Certainly many more factors come into play here, but in this case the total 
mass of the top bichord on the bass bridge and that of the lowest trichord 
on the long bridge might conceivably be similar, especially since on all 
but the longer grands there is a fall-off in tension towards the bass at 
the break, often to about 120 lbs.  A large increase in tension is required 
as the transition is made to the top bichords in order to compensate for 
the increased flexibility (decreased stiffness) of the covered strings.

As to "blending the tone", by which I understand matching as far as 
possible the harmonic balance of the adjacent break notes and not merely 
avoiding the most shocking of breaks, here the actual design and details of 
manufacture of the strings also plays an important part.  I heard someone 
say not long ago in front of an audience that a piano needs to be 9'6" long 
in order to achieve a satisfactory break between steel and covered strings!

The transition from plain trichords to covered trichords on the long bridge 
can be quite problematic and piano-dependent.


JD