It will be interesting to hear what others say, but here are my
thoughts on how to go about identifying unknown tunes, assuming you
can't find any documentation about the contents of the cylinder, disk,
music roll or recording in question.
First try to determine when the object was made. The earlier it can be
dated, the more thousands or millions of tunes that can be eliminated
from consideration. That makes for a smaller haystack in your hunt
for the needle.
Then try to determine whether you are dealing with European tunes or
American tunes as two broad categories. Next, determine whether you
are dealing with old standards or with the pop tunes of the year when
the arrangements were made. These two determinations may only be
possible when you are dealing with a fair number of tunes and can
already identify a few of them. The more you know, the easier it
becomes to fill in the missing pieces.
Finally, make audio recordings (cassette or MP3 or the like) and get
them, by mail or Internet, to people who are familiar with the type of
tune you have narrowed your unknowns down to.
The general Internet populace is of little help for tunes that are
really old, because to the relative youngsters who are net-savvy, an
"oldie" is a tune from the 1960's or so. Most have never heard of
Tin Pan Alley, Irving Berlin, or Walter Donaldson. This is gradually
changing, however, as sites specializing in ragtime, jazz, marches, old
sheet music, etc., spring up -- sites like Johns Hopkins University's
Levy Sheet Music site, Perfessor Bill Edwards' ragtime site, the
fascinating Parlor Songs site of Bob Maine and Rick Reublin.
The people who I have found to be most knowledgeable about the music
of the old days are musical collectors -- people who collect and are
familiar with 78 rpm records, piano rolls, sheet music, etc. from the
past. Some, like MMD's Frank Himpsl, rise eagerly to the challenge and
are delighted when they can nail down another unidentified tune. Fox
trots are fairly easy to identify, as a rule; the newer they are, the
easier they are. Waltzes seem to be the most difficult, probably
because they were danced rather than sung and often had no words to
stick in one's memory.
Making your job easier is the fact that what got arranged for
mechanical music use was -- at one time, at least -- popular with the
public. Making it difficult is the sheer quantity of tunes that have
been written, adapted, arranged, and forgotten. And sometimes one tune
is imitative of another, either deliberately or unconsciously, as in
the case of "Ka-Lu-A" and its predecessor "Dardanella".
It can be tricky, but it can be done, if you are persistent.