GETTING THE MOST OUT OF YOUR SAMPLER

By MIKE ARCHER. Edited by PARASITE.


        There's no doubt that the quality of the samples you make on your
Amiga is very dependant on the sound sampler you are using, however, I'm
not going to write an article on the quality of various sound samplers,
mainly because I have only ever used one sampler on the Amiga. (Any firms
out there who want to send me a free sampler to review are welcome to!!)

        No matter which sampler you own, there are quite a few ways of
improving the quality of the sample it produces. Most manuals that come
with samplers merely explain how to operate the features of the sampling
package provided, and not the correct way of going about making a sample
of clear quality. Following are some hints and tips on how to reduce
distortion and background noise...

INPUT VOLUME
        Many sampling packages provide a feature to view the waveform in
real-time like an oscilloscope. This feature isn't just a fancy graphic
equalizer to rig up to your hi-fi (Though it does make a damn good one!)
You should always use this display before making a sample to adjust the
volume of the sound you are sampling. The volume should be set so that the
waveform shown just reaches the top and bottom of the display, but doesn't
go off the display at all.

        If your input volume is too loud then when you sample the sound the
top & bottom peaks of the sound wave will be cut off, this causes very bad
distortion.

        If your input volume is quiet then the background noise produced by
your sampler will be heard. To my knowledge all samplers currently available
produce some background noise while sampling. The louder the volume you
sample at the more this background noise is drowned out.

        If you are sampling a quiet instrument, you should still adjust the
input volume as above, then use the volume controls in the music package
you are using to make that sample quieter than the rest.

CUTTING OUT THE INSTRUMENT
        Once you have made a sample, and you come to cut out the part of
the sample you wish to save and use as an instrument in your music program,
you should always ensure that the wave at the start and end of the sample
are both zero. In other words, always cut out the sample from/to a point
where the waveform crosses the center line. Doing this will vastly reduce
any clicking noises that occur when a sample starts/finishes playing.

SAMPLE RATE
        The sample rate you use is really up to you, the faster the sample
rate the clearer the samples produced will be. But they will also use up
more memory, it's really up to you to decide how much quality you are
willing to sacrifice to save memory.

        If you are sampling a musical instrument that you intend to use
along with other samples of other instruments, it is very important that
your sample is in tune. The easiest way to ensure this is to use a sample
rate which is the same frequency as the note you are sampling. Below is a
table of what sample rates match up to what notes. For example, if you are
using a sample rate of 338, you should play an 'E' on the instrument.

        NOTE    SAMPLE RATE     FREQUENCY (Hz)

  Middle C          427             261.7
         C#         404             277.2
         D          381             293.7
         D#         359             311.2
         E          339             329.7
         F          320             349.3
         F#         302             370.0
         G          285             392.0
         G#         269             415.3
         A          254             440.0
         A#         240             466.2
         B          226             493.9
         C          214             523.3

        If you wish to sample using rates not on this table then the table
can be easily extended by the following rule...  For each octave higher you
go the sample rate should be halved and the frequency doubled.

SAMPLING FOR REMIXING
        If you wish to remix a song by sampling short chunks of music and
piecing them together, you will probably discover that it is very difficult
to make it so a sample fits in with the tempo of the music program. Usually
your sample will end playing slightly before/after the next note is played.
(the next note usually being the next sampled bar of music.) This will
cause either a very noticeable click or a jump in the rhythm, depending on
how far out it is. The only way of getting round this problem is to slow
down or speed up the sample ever so slightly when it is played back.
Unfortunately most music packages will not support doing this, so we have to
get around the problem another way.
        If you record a sample slightly slower than the rate you play it back
at, this will effectively speed the sample up slightly. You could sit there
resampling the music over and over again at slightly different rates until
it fitted the tempo of your music program. This is what I used to do, how-
ever I decided there must be an easier way so I worked out a little
formula for use with sound tracker (and other clones).

n = ( tempo * 10000 ) / ( rate * 1.396825 )

TEMPO - This is the tempo setting you will be using in Sound Tracker.

RATE -  This is sample rate which you will play the sample back at, use the
        table given before to work the corresponding note to be played.

The value 'n' returned by this formula will be how many bytes of sample are
needed to fit exactly one note. So you must multiply this value by how many
notes your sample will last for. This will then give how many bytes long
your sample should be. Then it is a case of resampling at different rates
until the sample of the music is the required number of bytes.
        OK, I admit this still involves alot a messing around trying to
find the right sample rate, but at least you do not have to keep saving
your sample and trying it in Sound Tracker to see if it fits!