Re: Using Play command and polynomial tia sal2

• To: mathgroup at smc.vnet.net
• Subject: [mg97020] Re: Using Play command and polynomial tia sal2
• From: David Bailey <dave at removedbailey.co.uk>
• Date: Mon, 2 Mar 2009 05:22:35 -0500 (EST)
• References: <godm5p\$48c\$1@smc.vnet.net>

```ratulloch at gmail.com wrote:
> Greetings All
>
> I know the play command uses sin, cos, etc.  But I would like to use
> the Play command to listen to a polynomial.  Example below of
> polynomial
>
> Plot[Piecewise[{{4*x^2 - 4*x, 0 <= x <= 1}, {-2*x^2 + 8*x - 6
>     , 1 = x < 3}}], {x, 0, 3}]
>
> I replace the Plot command with Play
> Play[Piecewise[{{4*x^2 - 4*x, 0 <= x <= 1}, {-2*x^2 + 8*x - 6
>     , 1 = x < 3}}], {x, 0, 3}]
>
> but mathematica 6 just comes back with errors and
> just says running..
>
> I think it's syntax but I haven't found an example of using the Play
> command and Piecewise.  Should I be doing this another way?
>
> tia sal2
>
You had used = instead of == in one of the tests inside Piecewise.
Curiously, this did not cause an error using Plot. Here is a corrected
version:

Play[Piecewise[{{4*x^2 - 4*x, 0 <= x <= 1}, {-2*x^2 + 8*x - 6,
1 == x < 3}}], {x, 0, 3}]

Note that = means assignment, and therefore 1=x doesn't make sense -
which is what the message was trying to tell you - whereas == is a
comparison.

However, I am not sure I would pay to attend a concert in which the
result was playing :)

I think the result would sound more interesting if instead of playing
f[x], you played Sin[2 Pi f[x] x] with f scaled into the range of (say)
200-1000. The pitch of the resultant sound would represent the value of f.

David Bailey
http://www.dbaileyconsultancy.co.uk

```

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