Many packs on Splice Sounds include MIDI files. MIDI files are essentially note sequences (basslines, melodies, chord progressions, etc) that you can add to a MIDI track in your DAW, and play back using the virtual instrument of your choosing.
It's important to note that MIDI files don't actually contain audio information, and thus don't function the same way samples do. The audio you hear on the Splice website when previewing a MIDI file is just an example of one sound/instrument you may want to use to play back that MIDI file, so it won't sound like that right off the bat when you add it to a track in your DAW. If you're looking for a specific sound you heard in a MIDI preview, we recommend browsing our preset library!
Think of these files like ready-made piano roll sequences, which include velocity information and sometimes tempo/time signature data, that you can play back in your DAW using whatever MIDI instrument you want.
MIDI files on Splice typically cost 3 credits. As opposed to samples and presets, MIDI files from Splice download directly through your browser, to your computer's downloads folder. They don't download through the Splice app, and won't be visible in the app, but you can move/copy them to wherever you want on your computer once they've been downloaded.