Essentia has served in a large number of research activities conducted at Music Technology Group since 2006. It has been used for music classification, semantic autotagging, music similarity and recommendation, visualization and interaction with music, sound indexing, musical instruments detection, cover detection, beat detection, and acoustic analysis of stimuli for neuroimaging studies. A list of highlighted academic publications can be found here. Essentia and Gaia have been used extensively in a number of research projects and industrial applications.

  As an example, both libraries are employed for large-scale indexing and content-based search of sound recordings within, a popular repository of Creative Commons licensed audio samples. In particular, Freesound uses audio based similarity to recommend sounds similar to user queries. The Essentia extractor used for this functionality is in here. Also through the Freesound API the individual analysis descritors of a sound can be accessed. 
Dunya is a web-based software application using Essentia that lets users interact with an audio music collection through the use of musical concepts that are derived from a specific musical culture, in this case Carnatic music.
AcousticBrainz aims to crowd source acoustic information for all music in the world and to make it available to the public, providing a massive database of information about music for music technology researchers and open-source hackers. The project relies on Essentia for extracting acoustic characteristics of music, including low-level spectral information, rhythm, keys, scales, and much more, and automatic annotation by genres, moods, and instrumentation.
Good-sounds is a community-based online platform that allows musicians to automatically evaluate their playing exercises in terms of sound quality of instrumental sounds, their “sound goodness”. The evaluation is done by means of audio analysis technology Artistry developed by Korg and the bonus blog Music Technology Group and based on Essentia. The system measures how close the sounds performed by training musicians are to the ones that the community has identified as reference sounds.
Cortosia is an interactive tuner iPhone app using Essentia for automated evaluation of playing exercises by training musicians, developed by Korg and linked to the Good-Sounds platform.
MSAF Music Structure Analysis Framework is a framework for music audio segmentation using Essentia to extract the necessary features.
EssentiaRT~ EssentiaRT~ is a real-time subset of Essentia implemented as an external for Pd and Max/MSP.
ofxAudioAnalyzer ofxAudioAnalyzer is an openFrameworks wrapper for Essentia. It provides audio analysis algorithms modified to process signals in real-time.
Crypt of the NecroDancer is an award winning independent game. Players move on the beat of the music to navigate a dungeon and fight enemies. The game uses Essentia's beat detection capabilities to allow users to play the game with songs from their own music library.
Fretello is an app for iOS and Android that helps you learn guitar faster, more effectively, and permanently. It creates individual exercise regimens that are tailored to your specific needs, detects how you play, selects your optimal practicing tempo and adapts dynamically to your progress.