piyoDrums.bin is a set of extracted drum samples from
 Studio Pixel's PiyoPiyo, using a resource editor, Audacity, and this:

FileOutputStream fos = new FileOutputStream("piyoDrums.bin");
DataOutputStream dos = new DataOutputStream(fos);
for (int i = 0; i < 6; i++) {
 FileInputStream is = new FileInputStream("D" + (i + 1) + ".raw");
 int b = is.available();
 dos.writeInt(b);
 for (int j = 0; j < b; j++)
  dos.write(is.read());
 is.close();
}
dos.close();

Probably not a complicated format.

To be clear, the lengths are big-endian while the samples are 22050hz 16-bit little-endian.
Quirk of the conversion, no reason to change it without changing the whole format.

