---
title: "Helicopter 1 Sound Example"
id: 63148
type: "computer_media"
slug: "helicopter-1-sound-example"
url: "http://localhost/computer_media/helicopter-1-sound-example/"
markdown_url: "http://localhost/computer_media/helicopter-1-sound-example.md"
published_at: "2026-01-30T17:36:44+00:00"
modified_at: "2026-03-30T21:42:57+00:00"
author: "David Anderson"
featured_image:
  url: "http://localhost/wp-content/uploads/2026/01/helico-1.png"
excerpt: "A compact three-line loop drives the TS2068's AY sound chip through multiple registers simultaneously to recreate the thrum of a helicopter rotor."
category:
  - name: "Archived Media"
    slug: "archived-media"
    taxonomy: "category"
    url: "http://localhost/category/archived-media/"
post_tag:
  - name: "Downloadable"
    slug: "downloadable"
    taxonomy: "post_tag"
    url: "http://localhost/tag/downloadable/"
  - name: "TS 2068"
    slug: "ts2068"
    taxonomy: "post_tag"
    url: "http://localhost/tag/ts2068/"
model:
  - name: "Timex/Sinclair 2068"
    slug: "ts-2068"
    taxonomy: "model"
    url: "http://localhost/model/ts-2068/"
indiv:
  - name: "Kristian Boisvert"
    slug: "boisvert-kristian"
    taxonomy: "indiv"
    url: "http://localhost/indiv/boisvert-kristian/"
genre:
  - name: "Sound"
    slug: "sound"
    taxonomy: "genre"
    url: "http://localhost/type/sound/"
media_contents:
  - id: 63045
    title: "Byte Power September 1986"
    type: "computer_media"
    url: "http://localhost/computer_media/byte-power-september-1986/"
media_type: "Program"
programmers:
  - name: "Kristian Boisvert"
    slug: "boisvert-kristian"
    taxonomy: "indiv"
    url: "http://localhost/indiv/boisvert-kristian/"
mediadate: "1986"
producer_company:
  - id: 25181
    title: "Byte Power"
    type: "company"
    url: "http://localhost/company/byte-power/"
article_media:
  - id: 63031
    title: "Better Programming"
    type: "article"
    url: "http://localhost/article/better-programming-4/"
media_type_tags: "Sound"
---

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:

| Register | Value | Function |
| --- | --- | --- |
| 0 | 254 | Channel A tone period (low byte) — very low frequency |
| 1 | 7 | Channel A tone period (high byte) |
| 2 | 255 | Channel B tone period (low byte) |
| 3 | 7 | Channel B tone period (high byte) |
| 4 | 255 | Channel C tone period (low byte) |
| 5 | 7 | Channel C tone period (high byte) |
| 9 | 16 | Channel B amplitude — envelope mode enabled (bit 4 set) |
| 10 | 16 | Channel C amplitude — envelope mode enabled |
| 8 | 16 | Channel A amplitude — envelope mode enabled |
| 7 | 56 | Mixer: %00111000 — all tone channels enabled, noise disabled |
| 12 | 2 | Envelope period (low byte) — fast envelope cycle |
| 13 | 0 | Envelope shape — single decay (sawtooth down) |

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.

## Source Code

```
   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
```