Favourites from the "golden age": SHOW BOAT, PORGY & BESS, OKLAHOMA!, CAROUSEL, KISS ME KATE, THE KING AND I, GUYS & DOLLS, MY FAIR LADY, GYPSY, CABARET
Favourites 1970+: COMPANY, CHORUS LINE, CHICAGO, SWEENEY TODD, EVITA, SUNDAY IN THE PARK WITH GEORGE, LES MIZ, CITY OF ANGELS, GRAND HOTEL, RAGTIME
Age should certainly not be a factor in one's knowledge of musicals from before they were born. There are scripts, cast albums (for most musicals since OKLAHOMA!) and movie versions of varying fidelity. There are, however, some who do not know the older shows because they haven't had a chance to discover them as yet.
If you don't know any of the shows listed above, check your library for cast recordings and scripts. All of the above are well worth exploring.
Cast albums are NOT "soundtracks."
Live theatre does not use a "soundtrack." If it did, it wouldn't be live theatre!
I host a weekly one-hour radio program featuring cast album selections as well as songs by cabaret, jazz and theatre artists. The program, FRONT ROW CENTRE is heard Sundays 9 to 10 am and also Saturdays from 8 to 9 am (eastern times) on www.proudfm.com