Most DAWs have an FM synth of some sort. Set your output operator a few octaves (I usually go 3). Make an X bar long midi note for your buildup. Turn on another operator and route it into the first one. Set two automations: One for the amplitude of the modulating operator, the other for the ratio or frequency of the modulating operator (I've seen this work best with ones that have a single numbered ratio/Hz option like Sytrus and FM8, it's possible but takes some extra work with Operator) in one of the finer increments (hundredths, thousands, ten thousandths). Then increase both over the length of the bar. Mess with the curves and times and you've got yourself a pretty trippy riser!