Helicopter 1 Sound Example

This program produces a sound effect using the TS2068’s built-in SOUND command, intended to simulate a helicopter. The SOUND statement at line 10 configures multiple registers of the AY-3-8910 sound chip in a single statement, setting tone periods, noise periods, mixer, amplitude, and envelope parameters across registers 0–13. A short PAUSE 3 (approximately 0.18 seconds at 50 Hz) follows before the program loops indefinitely via GO TO 1, which uses VAL-less direct line referencing to a non-existent line, effectively halting or restarting. The REM at line 0 contains the program title, author attribution (K. Boisvert), and copyright notice for Byte Power (1986).

Program Structure

The program consists of just three executable lines plus a header REM:

1. 0 REM — Title, author, and copyright banner stored in the REM payload.
2. 10 SOUND — Configures the AY-3-8910 chip with a multi-register SOUND statement.
3. 20 PAUSE 3 — Introduces a brief delay (~0.18 s at 50 Hz) between sound restarts.
4. 30 GO TO 1 — Loops back; line 1 does not exist, so the interpreter finds line 10 as the next available line, restarting the sound effect continuously.

AY-3-8910 Register Usage

The SOUND keyword writes directly to named AY chip registers in register,value pairs separated by semicolons. The registers programmed are:

All three tone channels are set to nearly identical, very low frequencies (period ≈ 0x07FE–0x07FF), producing a deep drone. Envelope mode on all amplitude registers (value 16, bit 4 set) ties each channel’s volume to the shared envelope generator. The short envelope period (register 12 = 2) and shape 0 create a rapid amplitude decay that repeats as the loop restarts, mimicking the periodic thwop of rotor blades.

Notable Techniques

• Multi-register SOUND in one statement: All 12 register writes are chained in a single SOUND keyword call, which is more efficient than separate calls and ensures near-simultaneous register updates.
• GO TO non-existent line: GO TO 1 targets line 1, which does not exist. The TS2068 BASIC interpreter responds by jumping to the next line numerically above 1, which is line 10. This is a common size-saving trick.
• Envelope shape 0 behaviour: Writing to register 13 resets the envelope generator, meaning each pass through the loop re-triggers the envelope attack/decay from the beginning, reinforcing the rhythmic chopping sound.
• PAUSE 3: At 50 Hz, PAUSE 3 waits approximately 60 ms, controlling the repetition rate of the envelope re-trigger and shaping the perceived rotor tempo.

   0 REM                                                            HELICO                          WRITTEN BY K. BOISVERT          ©1986 BYTE POWER                     
   10 SOUND 0,254;1,7;2,255;3,7;4,255;5,7;9,16;10,16;8,16;7,56;12,2;13,0
   20 PAUSE 3
   30 GO TO 1