Simple and beautiful. Try this:
Oscillator: Sine
Voices: Poly. 6 or more.
Amp Envelope: Set Attack to almost-zero, to create the little “pop” transient. Set Sustain to zero. Then make both Decay and Release long, around 5 seconds.
Filter: Low Pass, Cutoff all the way up. We just want a bit of saturation from the filter, so bump up the Drive. We don’t want it to distort, but instead just add a bit of harmonics to warm it up, and give it a bit more tone.
Reverb: Big size. Pretty wet, around 50%.