The Key of Eb, from the Melody

Eb major harmonises to Eb – Fm – Gm – Ab – Bb – Cm – D°; D# minor to D#m – E#° – F# – G#m – A#m – B – C#. A son in this key mostly alternates the tonic and the dominant; a ranchera adds the subdominant; a bolero reaches for the submediant and the supertonic on its way home.

In the melody section this instrument is the melody section's written line — several players bowing one part together, so intonation is a group problem before it is anybody's solo. A chord on a bowed neck is really a choice of double stops drawn from these tones, plus the arpeggio a bow can walk through the rest — and a section playing in unison has to agree on which one, because two answers at once is a chord nobody wrote.

Learn the tonic, subdominant and dominant in Eb until the hand goes there unasked, and the repertoire in this key is largely playable before anybody names a form.