The document summarizes the process of reverse engineering a proprietary drum machine sample format called .D4T to understand its structure and write a script to convert the files to an open format like AIFF. Key details discovered include: - .D4T files store 32-bit floating point samples between -1 and 1 - The header includes the file size in bytes using a binary-coded decimal encoding, number of channels, and sample rate also encoded in BCD - With this information, the document author was able to write a Python script to properly extract samples and metadata from .D4T files and write them to an AIFF file.

1. Reverse-engineering a proprietary sound sample format: A detective story Andrew Bulhak http://dev.null.org/acb/