@Everybody Hates Me,
Everybody Hates Me wrote:Should I play the trumpet or the bass guitar?
Have you played either instrument?
If not, start by trying both of them out. On a very very general basis, bass guitar is easier as not everyone has the right embouchure to be proficient on woodwind or brass instruments.
Whichever is determined to be best for you, you will need to play well before you become involved in a band.
Keep in mind that if you are much past the age of 12, it is likely you would start as a band member, not a band leader.
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1. go to a music store, or to the music program at your school (if you have one). Try both instruments.
2. take lessons in the one that is determined to be best for you.