Taking a ferry from Sweden or Finland to Tallinn is a good option for people with large instruments.
If you do not have a car: From passenger terminal D you can use bus line no. 2 to go to the Tallinn coach station. Bus line no 2 runs between the passenger terminal D (Bus stop: “Reisisadam D-terminal”) and the airport via city centre.
Going to the Tallinn train station (Baltic Station/Balti jaam) requires a bit more walking and taking a tram or changing buses.
Adventurous people with cars might also look for ferries meant for trucks and freight transportation. It is totally on your own risk…