YOW, YOW2, and YOW3; three ear-catching sound effects, by Joe Horn.
Uses the SOUNDER program by Joe Ervin (included in this directory).

Joe Ervin's nifty SOUNDER package makes it easy to create great sound
effects.  [Later note: It's even easier to use Fatri's SoundKit, also
on this disk.]  Although it's not strictly possible to create chords
(two different frequencies or notes at the same time), the "effect"
can be pretty well faked by careful manipulation of the repeat loops.

For example, a constant frequency played for a long duration sounds
like a clean, single note, but if you instead play that frequency in
tiny bursts of varying duration, you'll hear two notes at the same
time, namely the constant "real" note, plus a "fake" note caused by
the interference of the ticks between each burst.  If the bursts are
brief enough, the ticks become a very audible buzz on top of the note
being played.  Varying the duration of the bursts varies the frequency
of the buzz.  Sort of an audible moire pattern.

The YOW and YOW2 example sounds in the YOW directory carry this
concept one step further.  Not only does the buzz go up and down in
frequency, but the "real" frequency is simultaneously changed, going
down and up (opposite of the buzz).  YOW2 is the same as YOW but
slower and wider, so you can really hear what it's doing.  It sounds
like a toy slide whistle to me.  You can actually hear the frequencies
going up and down at the same time!

YOW3 sounds outrageous because it combines the YOW2 idea with the
SWEEP command in SOUNDER.  It is basically a bunch of tiny sweeps
upwards, with each sweep's frequency interval being slightly lower
than the previous sweep, so it's going up and down at the same time.
Then it reverses, sweeping down as the frequency intervals go up.
And so on, for several loops.

To create your own effects like this, see SoundKit by Fatri on this
disk.