This is my own work.

Abstract: The program blends 16-bit wav data. It does not process the 44-byte wav header; it only blends the raw wav data, thus you have to cut the 44-byte wav header manually before the blending, and then add the 44-byte wav header back manually after the blending.

NOTE: The program can't handle files larger than 2GiB.

Usage: wav_blend_16bit <wav_source0> <wav_source1> <wav_destination> <alpha>

The blending is
destination_sample = (source0_sample * alpha + source1_sample * (1024 - alpha)) / 1024