This tune is in 5/4 time in the E-flat minor key.
Just two chords apart from a bridge which is a cycle of fourths.
Concert Eb | Bb
Bb Sax part F | C
E-flat minor is a minor scale consisting of the pitches E♭, F, G♭, A♭, B♭, C♭, and D♭.
In the harmonic minor, the D♭ is raised to D♮. Its key signature consists of six flats.
It could be easier on flute, but might sound better on soprano sax
Dave Brubeck's classic, Take 5 uses only two chords throughout,
for both the main melody and the subsequent improvisations.
It's in a minor key (we've chosen F here, but the original the more challenging Eb)
and the whole piece rocks back and forth between chords I and V of the scale - F and C,
only instead of the traditional major chord on the fifth, we have instead a minor 7th.