Commodore 128D - SECTION 8 - Using 80 Columns

j I
I I
; j
CUTOFF
FREQUENCY
Figure 7-10. Notch Reject Filter
.You can also add either the low-pass or high-pass filter to the band
pass filter to obtain interesting effects. By mixing the band-pass filter
with the low-pass filter, you can select the band of frequencies
beneath the cutoff frequency and below. The rest are filtered out.
By mixing the band-pass and the high-pass filters, you can select the
band of frequencies above the cutoff frequency and higher. All the
frequencies below the cutoff are filtered out.
Experiment with the different combinations of filters to .see all the
different types of accents you can place on your musical notes and
sound effects. The filters are designed to perfect the sounds created
by the other components of the SID chip. Once you have created the
musical notes or sound effects with the SID chip, go back and add
the FILTERing to your programs to make them as crisp and clean as
possible.
Now you have all the information you need to write your own musical
programs in Commodore 128 BASIC. Experiment with the different
waveforms, ADSR settings, TEMPOS and FILTERing. Look in a book
of sheet music and enter the notes from a musical scale in sequence
within a play string. Accent the notes in the string with the SID con
trol characters. You can combine your Commodore 128 music syn
thesizer with C128 mode graphics to make your own videos or "mov
ies " complete with sound tracks.
153
USING C128 MODE—Sound and Music in C128 Mode