Korg DSS-1 Owner's Manual page 40

Each sound is transposed up and down from its
original key value to cover the notes within its assign*
ed range. This pitch transposition is achieved by
varying the rate at which the data is read from
memory.
Since the sound data w as sampled at a particular
rate (the sampling frequency) when we recorded it (or
stored it), we can change its pitch by retrieving it at a
different rate. To transpose the pitch upward, we use
a higher read-out frequency than the original sampl­
ing frequency. To transpose downward, we use a
lower frequency than the original sampling frequen­
use same
cy. If we the frequency as the sampling fre­
quency then there will be no change in the pitch. (The
same sort of thing occurs with a tape recorder if you
change the playback speed.) Note that the lower
down you transpose, the rougher you waveform
becomes— this may be an audible problem if you use
the same sound sample over a wide range.
When you assign a sound to the keyboard, you set
the original key to the sam e pitch (frequency) as the
originally sampled sound. Then you set the top key to
the highest note to which you want the sound 's
pitch transposed. However, there is an upper "pitch
transpose limit" imposed by the highest readout fre­
quency available to the DSS-1. This maximum read­
out frequency is 64kHz and its relationship with the
sampling frequency is what decides how high up you
can transpose the pitch of a sampled sound. (Recall
that when you sample a sound, you have a choice of
four sampling frequencies to use. The relationship is
easy to see for the 32kHz sampling frequency. Doubl­
ing the retrieval rate raised the pitch an octave.) You
can refer to the chart here when deciding where to
set the top key for each of your sounds.
Particularly when reproducing acoustic instruments,
a reliable method is to take a sample from the same
note (F for example) in each octave. Then use each
sample for one octave of the DSS-1 keyboard. In this
case, you set the original key to the sam e note (F) as
the sample, while the top key may be assigned a half
octave higher (B). This gives you full, smooth
keyboard coverage.
If you use fewer samples, assigning each to a wider
area of the DSS-1 keyboard, then you may notice ab­
normal colorations and enveloping near the upper
and lower limits of each sound.
For high quality results it is best to use as many
samples (sounds) as possible, assigning each to a
narrow portion of the keybord, and thereby reducing
the required pitch transposition range for each
sound. This approach assures greater realism and
naturalness in the reproduced sound.
• Pitch transposition and data readout.
lower freq uency.
t
Pitch becomes lower.
(And playback time becomes longer.)
(You also start to hear the rough edges.)+becomes shorter,)
• Interval from original key to upper pitch transpose
limit,
Upper pitch
Sampling frequ­
transpose Limit,
ency of sound.
24 semitones up
I 6kHz
(64kHz)
17 semitones up
24kHz
(64kHz)
12 Semitones up
32kHz
(64kHz)
5 semitones up
48kHz
(64 kHz)
• Example: Making a multisound reproduction of an
acoustic piano.
/ ------- 7 ------- 7 ------- 7
0P 1
otct oi g w
^ ------ r - '; w r r
----------------------------- . .
------------ T *
.a
---------------- -
9 -
..................—
Piano sound will be reproduced at the pitch
corresponding to the key played at any
point throughout the keyboard range.
hig her f req uency.
;
Pitch becomes higher,
(And playback time
Exam ple using C3 as original
key, showing allow able range
of top key settings.
C 3 - C 5
C 3 - F 4
C 3 F 3
Sample these piano
------- 7------- notes.
Sounds obtained by
sampling.
Sound assignments
T0P
o k
and ranges.
Relationship between
original pitch and
transpose range.