Is the concept of 'intervals' in this sense any note in relation to the tonic note of the key, (whether that tonic note is being played at the time or not), or are melodic intervals just the immediate notes preceding the current note, regardless of key or other context?
So for example, in the key of C major...
if you play an F note, then a G note... does that mean this interval is the perfect second in between these two notes?
Or are these notes intervallic in relation to the tonic note of C?
In other words, is this F to G in the key of C a major second interval, or is this a perfect fourth, then a perfect fifth (C-F C-G)?