There are a number of royalty free web sites that offer midi clips and loops
for this. There are also CD library files available from various companies
that allow you to add music from them. These are licensed by the purpose,
which depends on how it is 'broadcast' (ie in a boardroom, classroom, PA
system, Gas station speakers at the pumps etc.) RIAA and SOCAN (in Canada)
have great information on this on their web sites. If you want real old music
beyond royalty limit times do a google search on 78 rpm royalty free music.
That music is freely downloadable and because of it's age, past royalty
requirments although quality is also pretty old.
Some editor software packages have sound built in, but you have to pay a
subscription fee to use it, and it usually only covers the use in the actual
production, any broadcast royalties for the music might be additional costs
on a per airing basis even.
If you have a MAC with "garage band" you might be able to create some loops
of your own as an original artist and use that; or if you have a friend that
is a band member that would be happy to give you permission to use their
creations just to get the web exposure that is also an alternative.
This whole area is pretty touchy one when it comes to royalties; better to
err on the side of caution and use something you know is royalty free like
garage band , a synthesizer, or a "good friend".
Good Luck
