What you would most definitively see among African Americans as a widespread, popular form of entertainment in the 1890s, and what would certainly be recognized in some capacity as "black music", was ragtime. The origin of ragtime is pretty obscure, although, as we know it from most publications, it is clearly a piano-based modification of the basic march form that was popular in the U.S. around that time (I.e, think John Philip Sousa), affected with distinct syncopated rhythms and a steady, "boom-chick", bass-chord backbeat, making it an all around very danceable style of music. Ragtime first makes it's appearance on the entertainment circuit in 1895 (With the first publication, if I am not mistaken, being 'La Pas Ma La' by Ernest Hogan, followed shortly by a piece by Ben Harney), and is probably not much older than that. So, in a way, above anything else, ragtime would be your go-to "black music" of the time. To dig further into your question, however, is tough. As laid out extensively in previous answers to similar questions, it's simply impossible to know much about African American music in every nook and cranny of the U.S. before the advent of electrical recording. Ragtime is an easy thing to point out, as it was a popular form of piano based music associated with the still thriving blackface minstrelsy caricature, as well as the burgeoning vaudeville circuit. Ragtime being piano based means that it can be fairly easily transcribed as sheet music, and something that is easily transcribed as sheet music will, in a pre-recording world, survive history in much more detail and much less shroud. The same can't be said for what might have constituted rural African American folk music and the such at the time (And many African Americans in the 1890s were still in the rural south, and this is often where we imagine as the birthplace of things like the blues). We do know to a degree as to what music rural African Americans would have played at this time, primarily thanks to early 20th century American ethnomusicologists like Alan Lomax (And his father, John Lomax) dedicating their lives to meeting rural African Americans and preserving what they suspected was music from an older time, and you can indeed hear African Americans play music that was from around that time. That all being said, that sort of music was a variety of different influences, with very little of it being particularly distinct to African Americans, being the sort of music you would have heard both white and black musicians play at that time. There is an undeniable black influence on that sort of music, but my point is, by the 1890s, that music was very widespread across America and would have been viewed as being just American music, rather than African American music in particular (That being said, "The Devil's Dream" recording might be of particular interest to you). When it comes to things like "proto-blues" and spirituals, we are even more impoverished on the actual nature and history of that in pre-20th century America. During the times of slavery, where we often imagine this sort of music would have been at it's height, the people who actually had the resources to document these things were not even remotely interested in doing so, and the ones who were, often didn't have the necessary education or resources to do so. There are publications, all the way from the 1860s, such as the book "Slave Songs Of The United States", published in 1867, which attempted to document the (Then acknowledged to be waning) music of formerly enslaved African Americans, and while it certainly tries it's best to document and describe things such as various forms of vocal music and ring shouts, it ultimately focuses more on the lyrics of these songs, where they might come from, and where the distinct aspects of slave music originates from, with less focus on actually trying to jot down any details that might help in reproducing the music for future listening and therefore understanding of what might have been heard in any capacity. This was just as true for the 1890s as it was for the 1860s, and there was just as little documentation of what rural African Americans were doing, musically. Blues as we know it from the 1920s til the 1950s is an entirely different subject almost, with the often accepted idea that the blues was a relatively unchanged form of African American folk music, or a simple evolution of it not being further from the case. Many recognizable aspects of things like the delta blues and Piedmont blues are distinctly 20th century additions to the music of African Americans. Delta blues was influenced by Spanish guitar (The open tunings) and Hawaiian slide guitar, and Piedmont blues is heavily rooted in ragtime. It's safe to assume that you probably wouldn't have heard much in the way of blues, as we know it, in the 1890s, with it likely having been a relatively novel thing to even see a rural southern African American play a guitar in a string band, let alone in the solo, unaccompanied style we often associate with the prewar blues masters. The instrument of choice of a southern African American before then would have likely been the banjo, and they would have likely been playing music like this. You can definitely see where influence on the blues likely came in from that, but it is only a part of the picture, and is still pretty far removed from the likes of a Charley Patton or Blind Blake, who were playing relatively new music at that point in time, despite what our 21st century ears might think.