Una corda piano

Isn't this one of the most inspiring instruments ever?: native-instruments.com/en/products/komplete/keys/una-corda/

It's unfortunate that instrument makers only sell high-priced packages that include five times as much stuff as you need. And that they use a locked down format like NKI. If you want SFZ or SF2 because you want to use your normal goto tools like polyphone, Musescore, or Timidity, too bad.

All a first world problem, but crowdsourcing produces amazing ideas so often.

Here's what I've tried as substitutes, any ideas?:

• plucked strings--pizzicato, plucked piano, folk or concert harp, psaltery, acoustic guitar. All vaguely reminiscent, but audibly not hammered.

• Christian Henson triple felt piano. The demos are strong, but in use too percussive.

• regular piano, played soft. Pleasant, but less mysterious-sounding. Maybe I just need to write more mysterious-sounding pitches. I should also scout out a dark, mellow instrument. A brilliant one is fantastic for Moonlight Sonata, not so much for a more intimate atmosphere.