This is probably the biggest music store complex in North America. I love this place!! It has everything and anything you could possible look for pertaining to audio, video, books, sheet music, guitars, basses, synthesizers, etc...in fact, 3 floors of them! Each different musical instrument has its own room where one could go and play around for hours sampling some pretty cool pieces. My favorite is the guitar and bass room. They let you play pretty much anyone you want and there are these neat little areas to try out multi-effects boxes and distortion pedals while connected to headphones. Definitely check it out!
The staff here are very knowledgeable and will help you find whatever you are looking for. Prices are pretty competitive, although with the current rate of exchange btw US/CAN, you would probably get a much better deal on guitars in the US. None the less, if you're in Montreal and into music of any kind, you gotta go spend some time here. One can easily spend half the day here as I have. Also, if your into electronic or house music, there is a small room downstairs off the main room that it solely for this genre of music, and they have some pretty hard to find titles which you can first listen to in the little kiosk before buying.