What is the default connection of notes in sheet music if there are no slur, staccato/tenuto/other marks: legato, portato... or something else?
I usually hear that a slur is needed to indicate legato, but if I just follow the exact duration of notes (for example exact 1/4 for a quarter note) and there are no rests between the notes, I get legato, because when the first note ends, the second note starts exactly at the same time. So, why do we need slurs to indicate legato?
There is no default. In the absence of markings, it's up to you to figure this out, just as you would have to figure out dynamics or fingering if those are left out.
For example, take a typical lead sheet for "How High the Moon": https://musescore.com/user/498481/scores/6477032, which leaves this out (ties are indicated as necessary, but no slurs).
There are lots of ways to play it, but "every note legato", or "every note disconnected" would both be a little weird. By default I think most people would group it into two or four bar legato phrases that end on the long sustained notes. (So, for example, you might add a break after the first B natural and after the following B flat).
It's notated this way because you're expected to be familiar with this kind of music and be able to figure out the phrasing on your own. The extra notation would be unnecessary clutter, unless for example this was some kind of teaching example, or a detailed transcription of one particular performer's choices.
Notation is needed only in cases where the writer wouldn't necessarily expect the performer to figure it out on their own.
As a performer, in the absence of notation, you're not going to get any hard and fast rule--you have to be familiar with the kind of music you're playing and listen for what sounds good, and there's sometimes quite a bit of room for creative choices.
Phrasing is something that cannot be precisely quantified. It can only be described by words like "legato" and "tenuto" and "staccato"
I tell my students to remember this: The music does not exist on the sheet of paper. The written sheet music is a detailed encoded message to help the musician figure out how to perform the music. The musician has to decode the messages and translate that into a live musical performance with instruments and voices.
Terms like "legato", "staccato", "tenuto" etc., and the use of the slurs, describe in words and pictures how to play a phrase of music.
Every note you play is going to have a starting point and a stopping point. If you play a series of notes (and this depends greatly on which instrument you are playing) there has got to be a tiny amount of silent space between most notes, or between some of the notes, when it becomes necessary to lift and reposition your fingers, or where you need to breathe air, or lift your bow or reverse your bow direction if you are playing violin, for example.
So you start out playing a phrase, a series of notes with no additional symbols to tell you how to connect them. You use the "default" phrasing that is appropriate to playing your particular instrument. For example, if you were playing a piano, and you examined the waveforms of an audio recording of your playing, you might find that you are holding each note for about 90% of the duration indicated by the note values. But this varies from note to note within the phrase. You need a small amount of empty space between each note to move your fingers and hand position.
The term "legato" means for you to try to connect the notes in such a way that they sound even more smooth and connected than the default. "Staccato" means to hold each note for approximately 50% of its notated value. And so forth.
These are all approximations, the "feel" of the phrasing. It's something you just learn through practice and through interacting with your music teacher and other musicians.
Depends on the instrument and performance practice. I disagree that notes lacking slurs in piano music default to legato; it also depends on the character and tempo. Assumptions are great inhibitors of creativity, interpretation and musicality. If you're talking about western art music, I'd recommend getting acquainted with some historical performance practice literature.
I must also disagree that legato will cause a change in phrasing. Merely detaching one slur from the next has very little to do with phrasing. Phrasing has more to do with pulse, dynamics, and rhetoric, than articulation.
To an extent, it's instrument dependent. On a piano, most 'ordinary' notes will be played legato by default. On wind instruments, each note may well be played using a separate breath/tongue. On strings it's different again. Bowing will make a difference in phrasing, so will need to be written. On guitar, a slur will indicate that the following note/s will not be plucked, but will be hammered on, pulled off, slid to, bent up/down etc.
Legato is not just about the length of notes.
When you play legato, you are trying to transition through the notes smoothly. This means you will also see a change in note velocity, volume and phrasing.
The difference is very instrument dependent. On a guitar, for example, you would try not to pick all the notes in a slurred series of notes, as the picking sound seems to split the notes up.
The default, with no markings, should have some separation, otherwise why would tenuto markings exist?
Also, we should listen to music: playing all notes full length does not have “no effect” nor does it have a “neutral” effect: its effect is long, smooth, or stretched out. In contrast, an effect that is “neutral” or “normal” has some separation, so it should be the default where no articulation markings are evident.
The "default" would be to play the full durations indicated.
That should not be confused with thinking there is no room for expressive interpretation. It is also a sort of "default" a performer is expected to give some expressive interpretation. Otherwise, performance is just a robotic activity, like a player piano roll, and the artist performer is irrelevant. How to interpret is the art of performance.
A lot depends on the era of the music. Compared with Renaissance to early Classical, the Romantic and Modern eras put more detailed expression marks/performance indicators into scores.
So, why do we need slurs to indicate legato?
Additionally, slurs indicate phrases. So there is more to it that just legato articulation.
