Harmonica: Harmonica is a better instrument to use, because it is relatively small, and its range is not very wide, so it doesn't need much skill and theoretical knowledge. Beginners can quickly master the basic operation and playing skills of musical instruments.
Guitar: Guitar is a very popular musical instrument. Beginners can learn basic chords and playing skills quickly, or they can get started quickly by self-study or following tutorials.
Electronic organ: Electronic organ can play many different timbres and styles, and can also teach itself through its own functions, so it is not difficult for people with a certain musical foundation to get started.
Flute: Flute is very popular in Asian countries. Because of its narrow range, beginners can quickly master basic fingering and playing skills without particularly high skills and theoretical knowledge.
Violin: Violin is a traditional western stringed instrument, which requires high skills and theoretical knowledge. Beginners need to learn basic knowledge such as fingering, bow technique and music theory, which is relatively difficult to get started.
The difficulty of the above instruments varies from person to person, and you need to choose the instrument that suits you according to your personal interest, music foundation, practice time and investment.