ABCmusic
ABCmusic is a tool for creating music by just using a pencil and a paper. You do not need any software for composing music in the ABC notation. ABCmusic uses characters for writing the music. If you look at a piano keyboard the white keys are named CDEFGAB for one octave. The black keys require two characters like ^C ^D ^F ^G ^A to represent them. The duration of the note is set by adding a number after the note. Here I write a small tune “Chicked dance”. Hopefully it helps to understand the concept of ABCmusic.
Once we have the melody working we have also defined the structure of the music. We now know how many bars there is and how the music phrases will repeat. This implementation does not parse segments and coda properly so the realtime playback is different from what I wrote. Sorry about it. Then we could have a look at the chords. There is two different chords in this tune. The chord “C” is the major chord and the “G7” is the fifth chord. As we plan to use only one note for representing the bass guitar we could use these two patterns for the chords.
Finally we can add wood blocks for percussion. The percussion would not have a pitch change at all so we can repeat the same pattern throughout the song.
When we combine these three sounds we get an irritating background tune that will annoy you just as much as the Flappy Bird game.
In Atari Lynx we use proprietary ABC codes to set the hardware for the tune. You can use these codes for changing an instrument on the fly also. Perhaps the first phrase is played by a flute and the 2nd by piano. I try to describe the recognized operators here.
T10 - Tempo - number of VBL interrupts that makes up a single time slot. The smaller you set this number, the faster the music plays.
X7 - waveform. This describes how the feedback links are connected to the polyphonic sound generator. - I don't get it either.
I0 - a letter I plus zero means a square wave, a one means a triangle wave. Triange has a smoother sound.
V100 - volume. Max is 127, min is 0
O2 - octave from 0 to 5. 5 is very low and 0 very high.
R0 - envelope ramp up
H0 - envelope hold note
K3 - envelope ramp down
These envelope parameters apply to the volume of a note.
In ABCmusic we need to code every one of these 3 melodies to a string. You can omit white space and bar lines without repeats to save space.
char *melody = “X7I1V127T10R6H10K1O2 G2 z2 g2 z2 | G2 z2 g2 z2 | G2 g2 G2 g2…”;
char *bass = “X7O2I1V100T10R0H0K3 D,4 G,4 | D,4 G,4 | D,4 G,4 | D,4 G,4…”;
char *percussion = “X7O4I1V40T10R0H0K6 D2 G G D2 G2 | D2 G G D2 G2 | D2 G G D2 G2…”
After this we can play the combined tune by making a call to abcplay()
abcplay(0, melody);
abcplay(1, bass);
abcplay(2, percussion);
The abcmusic drivers are available in different flavours:
- bll
- cc65
- newcc65
- in C-code