My friend told me that any piece would sound the same whether notated in 4/4 or 2/2 , even in 11/8 or 7/2 etc . ,
at the end its a type of measurement resembling a ruler where we agree on the value of one single measuring unit , like 1 centimeter or 1 inch , and then grouping every 10 centimeters , and so on..
I guess that mathematically he may be right , but my musical instinct tells me not ,
Can u help me understand this matter once and for all ,,
I'll take a bit of a stab at it (and who knows, it might even be true
Part of this mess is obscured in the dark, misty recesses of primordial music history.
In real olden days, the more white the page was (our half and whole notes and some no longer in regular use) the faster the music was. Pages with a lot of black notes would be slower. This often occurs still (the adagio movements with lots of 32nd note runs and fioraturae).
In the Baroque period, the time signature was often and indicator of tempo. Thus "C" (common time) would represent "tempo ordinario" -- roughly translated "Common Time". But there are strange (at least to us) inconsistencies -- often related to the type of movement. Thus 3/2 would indicate a slow, stately movement (unless it was a gigue/giga/jig in which case it would be rather quick.) Any thing over 8 would be a fast tempo (unless it was 6/8) and most things over 4 (4/4; 3/4) would be close to "tempo ordinario" (except when something else indicated otherwise. Thus cut time would indicate twice as fast.
While some of this has been lost over the years, there is a "learned" psychological aspect to it. Have you ever seen a 3/2 Vienese waltz (they are invariably 3/4, representing 1 beat to a measure), or a 6/2 march (6/8 is common)? When we see 3/2 or 4/2, "grave" or "largo" comes to mind. Similar for 2/2, though it is sometimes the march indication instead of "cut time".
6/8 adagios are common and they will often have 32nd notes involved, on the other hand faster 6/8 tempo will contain mostly eighth and dotted quarter notes (not enough time to play 32nd notes).
3/8 and 4/8 are usually associated with quick tempi and to some extent we often think of the "8" as indicating a lightness to it.
In the 20th century, it is reasonably common to see 8/8 (= 4/4, right). Usually when you see this, the composer is creating an odd division of the measure such as 3 eighths + 3 eighths + 2 eighths. (a kind of limping waltz).
Of course, meters with odd numbers on top will have odd divisions. 5/8 is 2+3 or 3+2, giving the effect of a limping march.
I will have to say though that 11/8 and 7/2 will never sound the same! 7/2 = 28/8 and 11/8 = 11/8. But it has only been in the 20th century that they have expected us musicians to count past 4 on a regular basis.
There are some books out there on the meaning of time signatures and tempi (though I can't think of any titles at the moment). If I find my notebook with that info, I'll post it.
Hope this helps.