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Four in A#
Four in A# — Miles Davis's crisp, up-tempo composition built on economical ii-V-I statements. Bebop Major over the tonic, Dorian on the iim7, Mixolydian on the dominant — every measure counts. Changes: A#maj7 – A#m7 – D#7 – Cm7 – D#m7 – G#7 – A#maj7/G – C#m7 – F#7 – F7 – Dm7.
Key of A#
A# (Bb) major requires barre chords rooted at fret 1 on the A string or fret 6 on the E string. Despite the barre demands, it is a common key in funk, New Orleans R&B, and brass band music. The open D string can ring as the major third for added color. A# is a intermediate-level key on guitar because the open D string is the major 3rd of Bb, adding a bright color if allowed to ring. Expect to rely on barre chords throughout, which builds hand strength and unlocks the entire fretboard.
Voice Leading
The bass line moves through A# to A# (ascending unison), A# to D# (ascending perfect fourth), D# to C (descending minor third), C to D# (ascending minor third), D# to G# (ascending perfect fourth), G# to A# (ascending whole step), A# to C# (ascending minor third), C# to F# (ascending perfect fourth), F# to F (descending half step), F to D (descending minor third). A half-step bass movement creates a strong leading-tone pull that demands resolution. The root motion by larger intervals (fourths and fifths) gives each chord change a strong, decisive character. When the progression loops, the bass returns from D to A# by major third.
Scales for Improvisation
A# major pentatonic works because every note is either a chord tone or a safe passing tone — there are no avoid notes. For soloing, this means you can play freely without clashing. Over dominant seventh chords, A# Mixolydian adds the flat seventh for an authentic blues-rock edge.