Jodeci have worker together since 95, but just hav not released al album. If you watch the DVD "Kci and Jojo - X" you will see Jodeci working on a new album but for some reason never came out.
They also appeared on a few different songs together (E.g. Dj Quick - Quickstrumental off Trauma)
Aaron Hall was a lead singer of Guy, very popular new jack swing group. In 90's he started to perform solo and released 3 albums. His style is similar to R. Kelly's or K-Ci's with strong powerfull voice and many slow jams.