Apple II PT3 Vortex Tracker Library

Library for playing pt3 files generated by the Vortex Tracker on an Apple II with Mockingboard.


This is an attempt to play some complex chiptune files on an old Apple II with a Mockingboard card. The Mockingboard, introduced around 1981, was a sound card for the Apple II series of computers. It has dual AY-3-8910 chips on it, providing a total of 6 channels of square-wave sound, plus noise and envelope effects.

My previous Chiptune Player played YM5 files, which are raw captures of the AY-3-8910 data stream. These are easy to play, but the raw data takes up a huge amount of space (hundreds of kilobytes) when uncompressed. The chiptune player did some clever tricks with LZ4 compression to make things fit, but in the end most of the 48k of RAM on an Apple II+ was needed to hold the ym5 file and decompressed register values.

This is coded in 6502 assembly language. And unlike my previous player, you can drop properly named files onto the disk image and they should play w/o any additional conversion.

Some technical details on the pt3 file format can be found here: README_pt3.txt

Some info on using the library can be found here: README.pt3_lib


Apple II Code/Disk Images

Using in Other Projects

Feel free to use this in your project! The code is dual licensed GPL2/BSD.

Some projects known to be using the code:

Development Log

29 May 2021

Released version 0.3 which adds support for Apple IIc.

This does make the library slightly larger, so you can disable this if constrained for space.

28 December 2019

Released version 0.2 which supports auto-detection of Mockingboard slot.
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