Its 404, yo!

It's 404, yo! is a tiny native macOS app that batch-converts sample packs into the exact format the Roland SP-404 MkII accepts on SD import: 16-bit WAV at 44.1 or 48 kHz. Drop in a whole folder, see in plain language what each file needs ("32-bit float to 16-bit", "FLAC to WAV"), and convert the lot in one click. Files that are already fine get copied untouched, and your folder structure stays intact. Fully offline and sandboxed, open source (MIT), and 99 cents on the App Store.