Does the Doppler effect work with some one playing an instrument?

if he played in tune would he still be in tune if he were moving back and forth like in the doppler effect

He’d have to move very far and fast for you to be able to hear the effect at all. If the musician just walks by in a marching band, you would nor hear the effect, because it is minimal. A highly sensitive tone frequency analyzer device could possibly measure it.

You can sometimes hear the Doppler on music in summertime when people drive with very loud music and their cars windows open. It sounds weird.

If a musician traveled toward you at half the speed of sound (about 380 MPH) their pitch would sound 1 octave higher. Likewise, if they traveled away from you at this speed they would sound 1 octave lower. There are 12 semitones or halfsteps to an octave. To sound one semitone higher or lower the the musician would have to be traveling toward or away from you at 1/24th of the speed of sound or about 32 MPH. In pitch 1 cent is 1/100th of a semitone. A musician at walking toward or away from you at a 3.2 MPH walking speed would sound 10 cents sharp or flat. This is certainly enough of a pitch change for a good musician to hear.

it works w/any sound

Absolutely! The doppler effect is simply the apparent change in pitch of sound or in intensity of light due to motion. Why do you ask? Did you hear a cheetah playing a saxaphone?