I am just starting to get familar with the meaning of notes and already read some related questions.
Lets assume I have a speed s of 60 "beats per minute" (bpm). Then one beat occurs during a time span of 1 s.
Lets further assume a piece that has a time signature of 2/4.
If I understand it correctly, by default the denominator is mapped to one interval (if not otherwise stated using an explicit tempo marker).
Therefore 1/4 takes 1 s. And a full note would take 4 s.
For a piece denoted in 6/8 at 60 bpm, 1/8 would take one second by default.
(Or is the default tempo mark not given by the denominator but another convention? For example a "dotted quarter" tempo mark for 6/8? If so, what tempo marks are mapped by default to what time signature? Is there some sort of lookup table?)
Now my actual questions:
A) Does the sound that I can hear when a 1/4 note is played take the full 1 s? Or can the sound be shorter (or even longer than that)?
With other words:
I. If the piece would consist only of 1/4 notes with the same pitch... would I hear only one continuous sound?
II. Or should I understand the time for a note value more like an interval where the sound is living in. The sound might start with an offset a from the beginning of that interval. Depending on the instrument or whatever (what exactly?), the length b of the sound can vary. There might be some time c of silence before the interval ends. The maximum duration of the sound is limited by the end of the interval (Is it or are sounds allowed to overlap?).
B.) If II. is true, what kind of notation and/or convention "has an influence" / is "used to specify"
C.) Is a always zero? Can a an c be negative? Do the notations only target a and b ... and c always automatically follows from a and b in combination with the interval length? Or do some notations target a and b and others c? Some kind of relation matrix of what notation/convention influences a,b,c would be great.
D.) Lets say we have two instruments with a fixed shape for the sound. The first shape is like a delta function, very sharp and short (e.g. 0.01 s). The second shape has long rising and falling parts, roughly like a triangle (0.4 s). If the two instruments would like to play together on the same notes, would I hear the maximum volume for the second instrument later than the first one, because both start with an offset of a = 0 at t=0? Or would the player of the second instrument start earlier, e.g. with an offset of a=-0.2 s, so that both reach the maximum at t = 0 (or better at t=0.5 at the middle of the note/interval?)?