Tape recording from the 1950's will be (for most practical purposes) about the oldest magnetic tape recordings you'll find. The very earliest ones are difficult to play because of the lack of formats and standardization of recording techniques. This is certainly not to say that these can't be played and transfered to a more current media with great success. There are a few of the members here who do just that for a living (archivists). Sometimes these tapes are fine and with the expertise of these professionals, the resulting sound can be quite remarkable. But if they've been stored incorrectly or been subject to severe conditions (flooding/uneven temps for example) the tapes will have to go through a restoration process before playing them. If these tapes are of any importance, personally, historically or musically, it's usually best to have them accessed by a professional instead of trying to "do it yourself" which could result in permanently damaging them.
If you have any interest in the history of American recording here's a link to some info about the founding father, Jack Mullin.
http://mixonline.com/mag/audio_john_mullin_man/index.htmlIf you wish to seek out an Archivist in your area, please feel free to PM me.
Welcome to our forum...(we use our real names BTW).