Chords that breathe.
Notes swell in rather than striking, like voices in a candlelit chapel. Hold three or four together and let them move; this is a sound for slow music, not fast playing.

Slow, breathing swells, like voices in a candlelit chapel.
No MIDI keyboard? Play with your computer keys: bottom rows are the lower octave, top rows the higher one. Hold Shift to sustain. ← → octave, ↑ ↓ semitone.
Online ambient organ
Notes swell in rather than striking, like voices in a candlelit chapel. Hold three or four together and let them move; this is a sound for slow music, not fast playing.
A MIDI keyboard helps most here: the sustain pedal lets you hold a chord and build the next one over it, which is how this sound is meant to move. On letter keys, hold Shift for the same thing.
It plays inside the page, with no download and no account, and nothing you play leaves your computer. Set the reverb to Cathedral and raise the mix while a chord is still ringing.