My favorite musical instrumenrt is piano.
correction:  My favorite musical instrument is the piano.

When I play the piano, Brian sings very well.  ✓

That voice and music are very good.
correction: His voice and the music sound really good together.

My father loves piano music.
correction: My father loves music from the piano.

When I play the piano, dad is sings too. ✓

That is why, my favorite musical instrument is piano. ✓

REMEMBER:
1. Be careful in spelling some words.
2. We always use *the* before the name of a musical instrument.
3. Let's arrange our words accordingly to make our sentences comprehensive
.

Hi, Ellie!
Thank you for the effort and I hope to see you again next meeting. Have a great time out there. Review the corrections I gave you!
-Teacher Joanna