...so it's almost C minor but with sixth degree raised half step
@awelotta's answer already points out the collection of tones is the Dorian mode.
But I think the more important thing that makes this almost minor - as in the key of
C minor - is not the sixth degree but the seventh degree.
The general minor family is first defined by a mediant (3rd degree) of a minor third. The supertonic (2nd degree) and submediant (6th degree) are the other mode determining degrees. The minor modes include Dorian, Phrygian, Aeolian (skipping Locrian.) All three will share a subtonic (seventh degree a full step below tonic.) To get the music into a proper key of
C minor the raised seventh degree is used.
G F B♭
F D A
E♭ C G
...that would be
Cm: v7 ii6 i6 in Roman numerals.
The important thing is the dominant chord -
v - is minor. It uses a
B♭ instead of a
B natural. That means the seventh degree is not raised for a leading tone. That is what really makes this not a minor key. It's modal instead. The sixth degree raised confirms Dorian mode. If the sixth was lowered, it would be Aeolian mode.
If the seventh was raised to
B natural and the dominant chord then had a major third, it would then put the music into a proper minor key.