About Harmonic Intervals. Can the notes have different sizes?

Question

I need to convert a MIDI file to a sheet-like structure. In the MIDI for the duration of the C#7 (dotted-quarter) the E6 plays twice (dotted-eighth and eighth) and the F#6 plays once (sixteenth).

If it helps. While the C#7 plays the sequence occurs : {E6(1/8*) ; F#6(1/16) ; E6(1/8)}

What I don't understand is the dotted-quarter duration of the C#7 note, every other note happens as noted in the sheet.

So what I want to know is if the notes in a Harmonic Interval can have different times, and how would I count it. And if the dotted-quarter duration is correct, how do I identify it?

PS: The time signature of this measure is 12/8

Answer 1

You've presumably got a double stop going here on the A and E strings at the second position. Yes, they sound at the same time, and you'll notice that the two voices actually take the same amount of time sounding together, a dotted crotchet (quarter note), although the lower voice breaks the dotted crochet into smaller pieces. If we notate it slightly differently, the relationship between the voices becomes clear:

You'll note that the metre of 12/8 is preserved. (Normally, the passage would be notated with up- and down-stems for the first beat, and the rests would omitted.)

Answer 2

The accepted answer is the correct answer to the question you asked, but your MIDI file isn't very accurate.

This is from the last movement of "Spring" in Vivaldi's "Four Seasons", and the original notation was like this:

The full score is here, if you have any more problems: http://imslp.org/wiki/Violin_Concerto_in_E_major,_RV_269_(Vivaldi,_Antonio)

Playing the C sharp as a full dotted-quarter on a real violin would be pointlessly difficult - Vivaldi knew what he was doing when he wrote the C sharp as an 8th note.