Musical Instrument
noun, の adjective
Remember how 楽 was used in 音楽 and meant "music"? Well this is that 楽 again. A music container is something that can produce music. It is a musical instrument.
がっき
This is a jukugo word, which usually means on'yomi readings from the kanji. You have already learned the reading for 器 but 楽 uses the secondary reading so you may not have learned it. However, you learned this reading in the word 音楽. Just bear in mind that the がく shortens to がっ.
これって何て言う楽器？初めて見た。
What's the name of this instrument? I've never seen it before.
楽器ってどこで買えばいいの？この辺りにお店ってある？
Where should I buy musical instruments? Are there any stores around here?
楽器にも色々ありますが、どんな楽器が好きですか。私は打楽器が好きです。
There are various different types of musical instruments. Which type do you like? I like percussion.