                            Ambulance 1.0
                          by  Nathan Sheldon
=======================================================================
    A patch for the Roland JV-1080, JV-2080, XP-50, XP-60 and XP-80.
=======================================================================

Overview:

I decided that I had to make a siren sound.  I felt challenged to do so
by some comments made on the JV-1080 e-mail list and felt I should give
it a try.  Though I'm sure there are other similar siren patches
available, I hope this one is just as good or better.  It is not quite
accurate, but closely resembles an ambulance siren (in the US) and
allows for it to come closer.

Requirements:

None (other than a JV or XP synth).  No expansion boards are required.

Control:

Use this:                 to do this:
----------------------------------------------------------------
Key-on Velocity           make the siren come on faster
Key-off Velocity          make the siren stop more quickly
Modulation                increase the siren's "distance" from listener
System Controller 1       make the siren oscillate faster
  (Aftertouch is default)

More Specifics:

This simple patch only uses one TONE.  The waveform is a Triangle
waveform and is put through a low-pass filter with a little bit of
resonance (to "highlight" a the mid frequencies).  The pitch is, of
course, oscillated by a LFO (Low-Frequency Oscillator) using a triangle
wave.  Though a real ambulance siren, it seems has a more downward
sawtooth type of shape, there is no such waveform with the Super JV
synths (only a downward sawtoothed wave that is too "sharp" for this). 
As an example, the following illustration demonstrates what I immagine
an ambulance siren's pitch to look like if graphed over time:

        -- Ptich of Siren Over Time --

  High -|  ______        ______        ______
P       |  |     \       |     \       |     \
I       |  |      \      |      \      |      \
T       | |        \    |        \    |        \
C       | |         \   |         \   |         \
H       ||           \ |           \ |           \
   Low -||            \|            \|            \
        +---------------------------------------------
        TIME -->

I could find no way to simulate this effect on the JV/XP synth, so I
used the next best thing (as illustrated below).

        -- Ptich of Siren Over Time --

  High -|      /\            /\            /\
P       |     /  \          /  \          /  \
I       |    /    \        /    \        /    \
T       |   /      \      /      \      /      \
C       |  /        \    /        \    /        \
H       | /          \  /          \  /          \
   Low -|/            \/            \/            \
        +---------------------------------------------
        TIME -->

This produced an adequate effect.  The sine wave was close, not the long
times in the low pitch (the trough) areas was too long and made it sound
less realistic.

Notes And Commnets:

Please feel free to comment on this patch.  You can use it freely
anywhere you wish and re-distribute it (along with this document)
anywhere.  It is, howver, Copyright 1998 by Nathan Sheldon.  :-)  If you
use it in any production that includes credits, please include my name
under synth programming.  I can be reached via e-mail at

nsheldon@geocities.com


Version History:

1.0  Initial release.
