The company posted yesterday on their Facebook page, the following statement:
As the official airline to nine of Canada's leading orchestras, we are announcing several industry-leading enhancements for passengers travelling with musical instruments. Customers may now purchase an extra seat for their instrument at a significant discount. Those travelling with instruments as carry-on items will have the opportunity to pre-board flights operated by Air Canada, Air Canada Express and Air Canada rouge in order to ensure their instruments are conveniently and securely stowed near their seat.
Read their complete policy regarding musical instruments here: http://www.aircanada.com/en/travelinfo/airport/baggage/music_inst.html