Can I play an instrument as a Muslim?

It depends on which scholars you follow. Most classical scholars held that musical instruments are not permitted, apart from the hand drum (daf) at weddings and Eid. Others, past and present, allow instruments when the music and setting are clean. Everyone agrees that playing must not cause you to neglect your duties or lead to sin.

The stricter view

Most scholars of the four schools understood the hadith about musical instruments as a prohibition. The Prophet ﷺ said that some people from his community would treat "illegal sexual intercourse, the wearing of silk, the drinking of alcoholic drinks and the use of musical instruments" as lawful (Sahih al-Bukhari 5590). On this reading, playing a guitar, piano, violin or flute is not permitted, whatever the tune.

The more lenient view

Other scholars, such as the early scholar Ibn Hazm and some contemporary scholars, point out that the hadith above is open to discussion and that the Quran does not name instruments. They argue that music is judged like any other activity, by its content, its setting and its effect on you. For them, playing wholesome music, such as a classical piece or a simple folk tune, can be permissible, while instruments linked to immoral gatherings are not.

The exception almost everyone accepts: the daf

The daf is a frame drum, similar to a tambourine. The Prophet ﷺ is reported to have said that what separates the lawful from the unlawful in marriage is the daf and the raised voice in song (Sunan Ibn Majah 1896). On an Eid day, when Abu Bakr objected to two girls singing in the Prophet's home, the Prophet ﷺ said: "There is an 'Id for every nation and this is our 'Id" (Sahih al-Bukhari 952). That is why wedding and Eid celebrations with a daf and singing are accepted by nearly all scholars.

What this means if you already play

You don't need to decide on day one. Many new Muslims keep playing while they learn the basics of faith, then reconsider.
Choose a view and ask an imam, because the answer you hear may depend on the school your local community follows.
If you follow the stricter view, you can still make music with your voice, a daf or percussion, or channel your skills into Quran and nasheeds.
If you follow the lenient view, keep to clean material and avoid venues with alcohol, immodest behaviour or songs that promote sin.
Think about your income. If music is your job, a scholar can help you plan a gradual change rather than quitting overnight.

Voice-only songs are a popular choice for people who follow the stricter view. See Are nasheeds allowed in Islam?

Common ground

Don't let practice crowd out prayer, work or family time.
Avoid lyrics about sex, drugs or disbelief.
Respect people who follow the other opinion; it's a genuine scholarly difference.

For listening rather than playing, see Can I still listen to music after becoming Muslim? and Can I listen to music while working out as a Muslim?

Key points

Scholars differ: most classical scholars forbid instruments, while some allow them under conditions.
The daf at weddings and Eid is accepted by nearly all (Sunan Ibn Majah 1896, Sahih al-Bukhari 952).
You don't have to throw away your instrument on day one.
Ask an imam, avoid sinful lyrics and keep prayer first.

Tip: Try a daf or a hand drum if you love rhythm. It is the one instrument almost every scholar accepts, and it is cheap and easy to learn.