Be careful of using any music, even if it's from the 30's.
In the UK:
Quote: "Copyright in a literary, dramatic, musical or artistic work lasts for the life of the author and 70 years from the end of the year in which he/she died"
and in the US:
Quote: "The duration of copyright has changed several times as Congress refined compromises over the law. Currently, [you] can generally presume that a work copyrighted less than 95 years ago is still covered by the law. ..."
Of course, the US lawmakers can't keep it simple, so there are loads of 'buts', 'excepts' and 'ifs', mostly paid for by Mr Disney and friends