Sorry to be always counterpointing you guys, but, yes! If you buy a fretless bass, as with a fretted one, the notes come first. To play a fretless bass doesn't require instruction. Just play the notes in tune. If you can't, then you have some practicing to do. If yo still can't, then your ear isn't trained to hear if you are in tune or not. It kind of goes back to tuning your bass with a tuner; when bass players realize that good time, an in tune instrument, playing a fettles in tune and any and all musical things comes from them, then they and the worldwide bass community will improve.I don't know if it's just me but I feel like bass instruction reaaaally comes short when it comes to fretless.
When you see what it takes a classical cello player to eventually play in tune... just buy a fretless and get down to it? Seriously?
People teaching or suggestion that fretless players need lessons is silly. You all know what to do. You have to play in tune So practice this.