If you mean ways of blending with them better, then there are many. All of them go back to what your mother used to say, "God gave you two ears and one mouth for a reason". 98% of music is listening. Everything you do in creating music should be aimed at supporting everything else, not overpowering or stealing the spotlight. Even solo artists must listen carefully to what's happening, comparing themselves to the ensemble and adjusting their voice to fit it. If you're singing backup for someone else, sing just loud enough so you can hear them equally as well as yourself. Match their voice as carefully as you can; listen for their dynamics, their timbre, and the shapes of their vowels. You can practice this by singing along with albums, but instead of doing it how most do (where they belt out with reckless abandon over the vocalist, adding their own flourishes) study the vocalist intently, matching everything (even the subtle nuances of their accent, but through listening to theirs rather than singing it how you think their accent should sound). The idea is to sound like one voice. If you want to know how to sing harmony, learn music theory and train your ear (again, listening is the key). Pick apart your favorite songs note for note, listening to the chord changes and the way the parts flow smoothly from one to the next. Usually your favorite vocal harmonies will follow choral-style arrangement (which dates back to the 16th century), which has fairly strict rules that create easy-to-sing harmonies that stack nicely together. This all takes a lot of practice, as well as changing the methods by which you practice - and it all assumes you have a good enough voice and ear to perform it properly. If you're willing to put forth the effort, the hardest thing for you to do will be training yourself to really listen - but it will pay off more than anything else.