I was first inspired to look into the meaning of "groove" after listening to a contemporary concert by Steve Mackey (contemporary composer and chair of the Princeton Music Department) and his students. Mackey is a brilliant modern composer, I recommend listening to his A Beautiful Passing. Anyway, I wondered what science had to say about groove, and found this:
JSTOR: Music Perception: An Interdisciplinary Journal, Vol. 24, No. 2 (Dec., 2006), pp. 201-208
The paper titled "Experiencing Groove Induced by Music: Consistency and Phenomenology" from Music Perception by Guy Madison discusses an experiment that tries to probe into the role of groove in music by having subjects rate pieces of music on various characteristics such as “groove, driving, simple, flowing, happy...bouncing, having swing”. Here is the abstract:
THERE is A QUALITY OF MUSIC THAT makes people tap their feet, rock their head, and get up and dance. The consistency of this experience among listeners was examined, in terms of differences in ratings across 64 music examples taken from commercially available recordings. Results show that ratings of groove, operationally defined as " wanting to move some part of the body in relation to some aspect of the sound pattern," exhibited considerable interindividual consistency. Covariance patterns among the 14 rated words indicated four prominent factors, which could be labeled regular- irregular, groove, having swing, and flowing. Considering the wide range of music examples used, these factors are interpreted as reflecting psychological dimensions independent of musical genre and style.They discovered that groove contributed to the second largest proportion of variation among all ratings, pointing to the importance of groove as a dimension of music (although they only included “music with a beat” in their music samples). And, they found that groove has no simple relation to tempo, or “having swing."
It’s interesting how science often seems to reduce and then expand artistic concepts. The paper starts by clearly defining “groove” as "wanting to move some part of the body in relation to some aspect of the sound pattern," but ultimately reveals that groove isn’t clearly attributable to any characteristic. So, I guess in the end, it all goes back to the elusiveness of “groove.”