Re: Choreography vs. Composition (and environments)

Darren Kelly (
Mon, 12 Jan 1998 11:04:35 +0100 (MET)


Dear Nick,

Nick (sensibly) wrote:
> > OK, but I think the term "filter" is misleading - it suggests that
> > information is being removed or rarified, rather than used in a
> > generative manner.

Darren prematurely replied:
> No, filter is exactly the right term.

[Note I'm sending this mail before reading your possibly scathing reply]

My apologies for hitting that nasty send key before I'd bothered to think.
I had a dream about filters and my reply the night after I wrote this &
discussed with a signal processing expert here at DESY the many possible
filters, amplifiers, distorters, transformers etc. that form the many
TRANSFER ELEMENTS in the chain of functions/operators that form the
TRANSFER FUNCTION that translates any signal input to a signal output. It
is an interesting exercise to consider the object-oriented class heirarchy
these elements form, and one immediately notices that filters form that
subclass of transfer elements that involve selecting/removing some of the
information from the signal (without actually distorting the remaining
information !):

>From the Macquarie Dictionary:

filter /'filtE/,n. ... 1. any device in which cloth, paper, porous
porcelain, or a layer of charcoal or sand, is held and through which
liquid is passed to remove suspended impurities or to recover solids.
2. any of various analogous devices, as for removing dust from air,
impurities from tabacco smoke, or eliminating certain kinds of light rays.
3. Colloq. a filter tip. 4. Photog. a screen of dyed gelatine or glass
used to control the rendering of coloour or to diminish the intensity of
light. 5. Physics. a device for selecting waves or currents of certain
frequencies only out of an aggregation including others. -v.t. 6. to
remove by the action of a filter. 7. to act as a filter for. 8. to pass
through, or as through, a filter. 9. to percolate; pass through or as
through a filter. 10. (of a a line of motor vehicles) to move in a certain
direction independently of the general flow of traffic. [ME filtre from
OF feltram "felt" (used as a filter) from Gmc; cf. FELT)

Not trying to defend myself here, but there is certainly some widespread
use of the term "filter" to denote general signal transfer elements. For
example, in the field of psychoperception the term filter is often used to
describe not only the limited amount of information the senses and brain
can perceive from the entire information impinging on a being's sensors,
but also (incorrectly) to denote distortion of that information, bias of
that information, optical and sensory illusions etc. I've even heard
"religious filter" to denote the biasing of information.

Also EQ elements should not be considered filters; in the case where,
for example, a treble knob enhances the treble, one should speak of a
selective amplifier. When a portion of the treble is reduced, the
signals is indeed being filtered.


Saturday over breakfast my girlfriend mentioned that in school she learnt
to use a feather pen and inkwell. We talked about how much writing tools
affect the way one writes and thinks. I fear I tend to write poorly with a
pen these days, backtracking and scribbling bits out as if backspace and
delete keys were available, instead of thinking before I write. My
grandma's letters were always spotless. I don't think I'd have made a good

Perhaps this is another reason I'm not much of a fan of citing newsgroup
and electronic forum archives; the net is perhaps more forgiving of
mistakes than other media. On the other hand, promoting the recognition
of citation of such archives might encourage dills like me to think before
they type and before they hit that perilous send key.

I'll read my email now,


Darren Kelly | | |
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