Code:
#include <amxmodx>
public client_putinserver(id){
set_task(0.3,"play",id)
}
public play(id)
{
if(is_user_connected(id)){
client_cmd(id,"mp3 play mp3\musica.mp3")
}
}
enjoy, you wanted to run this code "mp3 play mp3\musica.mp3". Therefore, i didnt add the precache part.
edit: i always forget to check if user is connected