stereophonic AK-900, Assembly And Instruction Manual

Page: 8 / 24

-7-
Now observe this tone:
The frequency is slowly increasing and decreasing in a regular pattern. This is an example of vibrato. If the
frequency is changing slowly then it will sound like a varying pitch; a fast vibrato (several times a second)
produces an interesting sound effect.
Tempo is a musical term which simply describes how quickly a song is played.
The Electronic Keyboard Implementation:
The AK-900 electronically creates sounds that closely resemble those from traditional musical instruments. A
quick look at the
schematic (a graphical representation of an electronic circuit) on page 17 will show the reader
that the IC 9037 is the heart of the product. This part is a 68-pin silicon Large-Scale Integrated Circuit made
with CMOS (Complementary Metal-Oxide-Semiconductor) technology. For more information about CMOS and
integrated circuits please refer to the references. Please refer to the schematic and the IC 9037 block diagram
and pin description on page 17 to help understand the following:
The IC 9037 is specifically designed for electronic keyboard applications. It generates a 523.252 kHz signal
which is used as a master timing reference for all operations. The 37 keyboard keys represent musical notes
C3 to C6 in the musical scale table shown earlier. These are connected directly to the IC 9037 and may be
played anytime. These tones are produced by dividing the 523.252 kHz reference down to the appropriate
frequency and then adjusting the levels of the overtones based on which instrument is being played. When you
play a note on an instrument the sound produced is initially rather loud and then decreases with time. This effect
is simulated in the envelope block in the IC 9037 and the resulting output tone also decreases with time. As
can be seen from the block diagram, there are two sets of the circuits just described to allow two notes to be
played at the same time; once additional notes are played the earlier notes will be discontinued. Since the two
most recent notes will be the loudest, this simplification from traditional instruments (such as a piano where the
strings continue to vibrate until played again) will not be easily noticed by the listener. More complex electronic
instruments will have more circuitry to simulate more notes at the same time as well as more advanced
techniques for producing overtones.