This won’t help you discover your ancestors but will help you learn about the music they enjoyed. Following eighteen months of work, more than 50,000 78rpm record “sides” from the Boston Public Library’s sound archives have now been digitized and made freely available online by the Internet Archive.
I am sitting here listening to It Had to be You by Jazz legend Art Tatum. The fidelity is what you would expect from a 78 rpm record made in 1944. That is, it is definitely low fidelity. However, it is obvious that Art Tatum was a keyboard maestro.
You can learn more about this new Boston Oublic Library’s additions to Archive.org’s collection of old music at http://bit.ly/2V5xVsm while the collection itself may be found at: https://archive.org/details/78rpm_bostonpubliclibrary.
Archive.org also has more than 5 million audio recordings available, starting with some of the very first recordings ever made on Edison’s wax cylinders up through more than 13 thousand Grateful Dead recordings from the 1960s through 1990s. You may find a few recordings by other artists in even later years. You can search the entire music collection by starting at: https://archive.org/details/audio.