I wouldn't focus too much on 'emotion'. Music is often a very technical thing. The issue is phrasing (i.e. breathing), watching the phrase marks and being specific on melodic gaps, think of subtle tempo changes, think of dynamic changes.
Sing the melody and see what you voice is doing. Take, for example, an actual song. Faure Claire de Lune. Sing the opening wonderful piano introduction, see how your voice rises and falls, see where you take breaths. See how you sing the semiquavers, they are not metronomic. See how you physically move your body during the phrases.
Then try to do the same on the piano. You will struggle, but at least you know what you want.
Music is often simply about learning to listen.
Gerald Moore is great. Listen very carefully to every little nuance he makes.
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This one is very different, but similarly you can analyse.
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Compare with this, a good amateur. Balance between hands is dodgy, it isn't always smooth, none on the subtle changes by note. Rushes around 24 secs. Remember the topic of the poem. Languid.
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When you can analyse and understand why Moore is so great, you are on a good road.
I picked this not because it is a song, but because the piano melody could be sung.