Bb Augmented (Bbaug)
Also written as A# Augmented (A# and Bb are the same key).
1+3+#5
Notes in Bb Augmented
A# (root)DF#
Inversions
Same notes as Bb Augmented, with a different chord tone as the lowest note. Useful for smoother movement between chords instead of jumping around the keyboard.
Root position
A# in the bass
1st inversion
D in the bass (Bbaug/D)
2nd inversion
F# in the bass (Bbaug/F#)
Bb Augmented consists of A#, D and F#, played at the same time.
Stretch the fifth of a major chord up by a semitone and the result is symmetrical: two identical major thirds stacked on top of each other. That symmetry means the chord has no clear sense of up or down, giving it a floating, slightly dizzying quality composers reach for when a moment needs to feel suspended or unresolved.