Tuning steel drums -Forwarded

[Inventrncs@aol.com]

I noticed some misinterpretation in the posting on the steel drums, and I
thought this would be a good time to break into the PianoTech list.
 Yesterday Kent Swafford wrote:


>        Partials:
>  Note    1st    2nd    3rd    4th   5th    6th    7th    8th
>   C5:    26.0   23.9   26.2   24.8  11.2   28.3   -7.0   24.0
>   G5:    21.3   24.3   28.3   23.3  11.3    NR     NR     NR
>   C6:    26.7   22.1   26.4    NR    NR     NR     NR     NR

>     (NR means the ETD couldn't get a reading at that level.)

>        As you can see above, there is inharmonicity but it is
>   inconsistent.  The partials of the two C's are "flat," and the
>   partials of the G are sharp.

And Michel LaChance responded by writing:


> I doubt a steel drum would have any inharmonicity at all.  I know a
xylophone
> maker who uses a Korg tuner and really doesn't care about partials
deviation.
> The best way to make sure of it is to measure a given pitch and then
measure
> its second partial.  If the latter has exactly twice the frequency, then
> there is no inharmonicity factor to care about.

> Michel Lachance, RPT
> Chance@cme.qc.ca

The chart that Kent Swafford posted shows that there is some negative
inharmonicity in the steel drum, and I will explain.  If C5 did not have any
inharmonicity then Kent's measurements would have come out like this:
  Note    1st    2nd    3rd     4th     5th    6th     7th    8th
  C5:    26.0    26.0   28.0   26.0  12.3   28.0   -5.2   26.0

Only the octaves fall nicely into place, the third, fifth, sixth, and seventh
partials do not fall into place due to the deviation of the equal tempered
scale from just.

Kent's chart (above) shows the following  for  the note C5:
  C5:    26.0   23.9   26.2   24.8  11.2   28.3   -7.0   24.0

Below is the difference between the two numbers:
  Note    1st    2nd    3rd     4th     5th    6th     7th    8th
 C5:      0.0     -2.1   -1.8   -1.2    -1.1   +0.3   -1.8    -2.0

The steel kettle demonstrates negative inharmonicity, except for the sixth
partial.

And as far as the Xylophone maker, he might sell more of his xylophones if he
was more concerned about where the partials were when he was manufacturing
them. There may or may not be a way to control the partials of a xylophone,
you will never know until you try.

I believe that you can control the partials of a steel drum.  We have a
manufacturer of steel drums that was talking with us about purchasing an
Accu-Tuner, but I can not remember his name.  I will be trying to remember
his name over the weekend, if I think of it I will post a note to David
Graham.

Sincerely,
Paul Sanderson
Inventronics, Inc.
Inventrncs@aol.com