Music Maker
Peter Collins, Springvale South, Vic.
 
While exploring new uses for the ’660 I decided to write a 'song’ using notes from the 'Song In the Key of Yale' program published with the Programming in CHIP 8 article, November 1981. This was fine, but how could I develop songs in different keys? I then decided to develop the following program to
assist. Keys on the keyboard are used to control the program and step through the tones, displaying the hex value of each note on the screen. Here’s what each key does:

KEY O: Tone generator starts at the highest tone and steps down in pitch.
KEY 5: Stops the tone at the step it is on.
KEY 1: Repeats the tone of a value displayed on the screen.
KEY 4: Manually increases the tone one step for each key press.
KEY 6: Manually decreases the tone one step for each key press.
KEY 2: Causes program to jump to song routine.

You can write a song by setting the duration of the tone required using Variable 1 (V1) and setting the tone using Variable O (VO). Then follow with a 'do tone’ instruction - 27BO if no space between tones is required, or 'do tone with space’ using 278C. If the tone duration and pitch are not changed a further `do tone' instruction will repeat the tone. If a change in either pitch or duration is required, or both, these are changed before the next 'do tone` instruction by settng the values of VO and V1 as required. Spaces are located in routines which can be called as required. A short space is located at 078E and 'special’ spaces are located at 0776, 077A, 077E and 0782 by setting V4 then jumping to a timer loop which controls the duration ofthe space.

