Korean Air · Small wind or brass

Yes

Cabin: yes

Within 115 cm in total it comes on board free.

You can buy it a seat on this airline.

Korean Air rules

Instruments with total dimensions (length + width + height) of 115 cm or less, such as violins, may be brought on board free of charge, in the bin or under the seat.
Over 115 cm, such as a cello, you must book a seat for it through the Service Center.
Korean Air recommends the cabin or a purchased seat over checking, because of the risk of damage.
A checked instrument must be in a hard travel case, and you sign a limitation of liability form at check-in.
Over 203 cm in total and 32 kg, it must have a seat or go as freight.

Before you leave for the airport

Measure the case and weigh it packed. Staff measure the case, never the instrument.
Check the fare. The cheapest fares often include only an under-seat bag.
Check who operates each leg. The operating airline's rule applies.
A seat for the instrument is booked by phone, often 48 hours or more ahead.
Photograph the instrument and case before you leave home.
Board as early as you can.