Increases in storage capacity and network bandwith coupled with advances in audio compression technology and computational performance have made possible the creation of large digital audio arhives containing thousands of hours of audio. The combination of audio signal processing and machine learning techniques has the potential to create sophisticated tools to interact with these large collections. Manual audio annotation forms a necessary and commonly tedious part of this process that is frequently sidelined in the published literature. By carefully combining basic practical ideas from machine learning and human-computer interaction it is possible to significanty reduce annotation time and improve the annotation experience without affecting the quality of training data. Specific examples from the annotation of Orca vocalizations, religious chants and popular music are provided.