Help identifying cadences and modes in iidim7 - i - vidim - vsus4

Question

I'm a beginner when it comes to modes and cadences, and I want to understand them better to improve my song-writing as a metal guitarist. While fiddling with my guitar today, I "wrote" this progression in the key of E minor (or the E Aeolian mode, if I'm right):

ii half-dim 7 --> i (Em) --> vi dim --> v sus 4

1. Could someone tell me what type of cadence occurs between the bars 1 and 2, and also between the bars 3 and 4?
2. If I understand correctly, only the modes have changed, because I have only used notes from the key/scale of E minor. But what modes are these?
3. Why does the vi dim --> v sus4 feel like it has been resolved? I thought tension is resolved only when we return to the root/home chord.

(P.S. I feel I've heard this progression before, maybe someone knows where it's from? :) )

Answer 1

This progression lends itself to a variety of interpretations, all similar, but varying in technical detail. This progression, even more so than others, is highly dependent on context -- chord voicings, melody, and what happens before and after.

ii7 - i (F#7b5 - E minor)

ii moving to i as a cadence does not itself have a specific name.

However, it is related to a plagal cadence, iv - i. Although not a plagal cadence it provides a similar sound. And iv - i is built in: the iv chord = A C E, and the ii7 chord is the same but with the addition of F#. We could consider the chord as Am6 rather than F#m7b5.

A somewhat different interpretation comes into play if the E minor chord is voiced with B as the lowest pitch. In that case, it might be considered a "cadential 6-4 chord", heading toward the V chord at the end of the progression.

vidim - Vsus4

vi moving to V also doesn't have a special name. The usual interpretation is that vi is functioning as a predominant moving to the dominant.

However, the "vi dim" chord "doesn't exist." That is, a diminished chord built on the sixth scale degree, C, would be spelled C Eb Gb, with the latter three tones being alien to E minor.

Instead, I think one of two things is happening:

1. Cdim is actually D#dim7 with the fifth omitted. That makes the chord viio7 in E minor. The reason, then, it sounds like a cadence moving to Vsus4 is that Vsus4 is actually isus2. Vsus4 = BEF#, and isus2 = EF#B: i.e., it is, in fact, a cadence ending on the (ambiguous) i chord!
2. Also possible is that both the "C diminished" chord and the "B sus4" chords are a single chord: B7b9sus4(omit7). Written in root position, this chord doesn't appear to make sense: BD#EF#C. But with better voicing -- for example, BECD#F# or EBD#F#C -- it becomes a V chord with the E anticipating the (unresolved) resolution to Emin. This is very Mozartean, placing the tonic below a dominant chord (before proceeding to the tonic chord). (Note: in Mozart's case, the "dominant over tonic" chord is likely a suspension from an actual dominant, where the bass resolves first followed by a delayed resolution of the rest of the chord.)

overall mode

The progression is solidly in E minor and uses pitches only from the E harmonic minor scale. However, it's an ambiguous E minor due to the absence of a strong cadence confirming the key.