How to sing Silent Night in your key
Silent Night spans 17 semitones (C4 to F5 in its usual key), 46 notes. That's wider than an octave, so most people need to pick the key carefully.
Words
Silent night, holy night,
All is calm, all is bright
Round yon virgin mother and child,
Holy infant so tender and mild,
Sleep in heavenly peace,
Sleep in heavenly peace.
Finding your key
A song is in your key when its highest note sits at or just below the top of your comfortable range. Measure your range, then move the melody so its top note (F5 here) lands one or two semitones under your easy top. Singsteady does this for you and scores every note as you sing.
1818 (Franz Gruber); English words 1859 (John Freeman Young). Melody and words are in the public domain. Notes transcribed from the score in Wikipedia, “Silent Night” (contemporary score).