A friend has one of those saddle type AC as suggested by @nonoise . It is pretty quiet. He said the added larger rubber bumpers to get a tight fight.
I have seen at working garages, where they have a unit far away and they "pipe" the cold air using hanging fabric ducts. Is that an option for you? Maybe piping from bedroom (and assuming you are single ha ha ha).
I use a Vornado to move air into my office. It moves a lot of air for its size but it is not quiet for a music room (at least not at full blast as it is running as I type this)