We introduce an audio retrieval-by-example system for orchestral music. Unlike many other approaches, this system is based on analysis of the audio waveform and does not rely on symbolic or MIDI representations. ARTHUR retrieves audio on the basis of long-term structure, specifically the variation of soft and louder passages. The long-term structure is determined from envelope of audio energy versus time in one or more frequency bands. Similarity between energy profiles is calculated using dynamic programming. Given an example audio document, other documents in a collection can be ranked by similarity of their energy profiles. Experiments are presented for a modest corpus that demonstrate excellent results in retrieving different performances of the same orchestral work, given an example performance or short excerpt as a query.