The Chinese word for harmonica is
口琴

kǒu qín

Chinese Definition

harmonica
1. 口琴
Components
口
1. (anatomy) mouth, especially the lips and internal mouth cavity
漱漱你的口。 (Shù shù nǐ de kǒu.) - Rinse your mouth out.
這話出自你的口，聽來令人奇怪。 (Zhè huà chūzì nǐ de kǒu, tīnglái lìngrén qíguài.) - This sounds strange in your mouth.
2. entrance; opening; mouth (of an object)
入口 (rùkǒu) - entrance
出口 (chūkǒu) - exit
門口 (ménkǒu) - doorway
3. gateway
張家口 (Zhāngjiākǒu) - Zhangjiakou
口北 (Kǒuběi) - the area beyond the Great Wall
口蘑 (kǒumó) - St. George's mushroom (Calocybe gambosa)
4. hole; cut
口子zi (kǒuzi) - hole
傷口 (shāngkǒu) - wound
5. port
電腦端口 (shāngkǒu) - computer port
Csēi口 (sēikǒu) - USB-C port
6. perimeter
人口 (rénkǒu) - population
戶口 (hùkǒu) - hukou
7. government organ; department
三口之家 (sān kǒu zhī jiā) - a family of three
我可以吃一口嗎？ (Wǒ kěyǐ chī yī kǒu ma?) - Can I have a bite?
8. (neologism, slang) to fellate
9. Variant of 名
琴
1. (musical instrument) qin (“Chinese zithers”), referring to any of several traditional Chinese musical instruments, most famously the guqin
2. (musical instrument) collective name for certain musical instruments, usually of string or keyboard types, such as piano, organ, violin, cello, huqin, accordion, harmonica, etc.
3. (musical instrument, specifically) piano (attn, zh, just Hong Kong?)
4. (Cantonese) yesterday