Video Tutorial: Adding Attack & Release to EXS/AUSampler instruments
UPDATE, 4/2/2018: The new AKSampler code released in AudioKit 4.2 allows for ADSR envelopes without setting up anything special in the source files. This video is mostly unnecessary now with the new features of AKSampler. Unless you want to use AVAudioUnitSampler. Then, these techniques still apply