Organ-AA and Organ-Ba

This document details two programs, ORGAN-AA and ORGAN-BA, designed for the PDP-12 computer to turn the keyboard into a musical instrument that plays through the system speaker.

• ORGAN-AA: This version allows the user to play in real-time like an organ. Each key on the keyboard is mapped to a musical note across a four-octave range.
• ORGAN-BA: This version is a simulation designed to play pre-stored melodies. The user stores a sequence of notes in memory, and the program plays the next note in the sequence each time a key is pressed, allowing the operator to control the tempo.

The document includes technical descriptions of how the programs manipulate bit 0 of the Accumulator to generate sound, instructions for operation, and complete source code listings (PAL III) for both programs.