help on a particular sheet music notation - clair de lune

Hi,

I have a question about how the notes in a piece I'm learning are written in the sheet music.

In the 11th measure of clair de lune, the second beat in is a chord of D and high D, with an A (stem down) just before it. Listening to this piece, I hear the three notes played together, so why is the A not on the stem with the surrounding D notes? Why is it on a separate downward stem? This appears a few times in the piece. I'm confused.

Thanks.

 

The A is a quarter note, while the D (and E) octaves are eighth notes. Therefore, A and D-D are played together but the A must be held until the next beat.

 

Thank you - I had never come across this before.