The pitch class the track is in. This metric also lists if the song is played in a major or minor key. Why is this important?

The time signature (meter) is a notational convention to specify how many beats are in each bar (or measure). You can find examples of different time signatures here.

The overall estimated tempo of a track in beats per minute (BPM). In musical terminology, tempo is the speed or pace of a given piece and derives directly from the average beat duration.

The overall loudness of a track in decibels (dB). Loudness values are averaged across the entire track and are useful for comparing relative loudness of tracks.

Loudness is the quality of a sound that is the primary psychological correlate of physical strength (amplitude). Values typically range between -60 and 0 db.

Energy is a measure from 0 to 100 representing a perceptual measure of intensity and activity. Typically, energetic tracks feel fast, loud, and noisy. For example, death metal has high energy, while a Bach prelude scores low on the scale.

Perceptual features contributing to this attribute include dynamic range, perceived loudness, timbre, onset rate, and general entropy.

A measure from 0 to 100 describing the musical positiveness conveyed by a track. Tracks with a high number sound more positive (e.g. happy, cheerful, euphoric), while tracks with lower number sound more negative (e.g. sad, depressed, angry).

Danceability describes how suitable a track is for dancing based on a combination of musical elements including tempo, rhythm stability, beat strength, and overall regularity. A value of 0 is least danceable and 100 is most danceable.