Generally, when is it justified to play a string of notes and only use one down or up bow?
Example: Say the music wants you to play, b (quarter note),c (quarter note), and d(half note) to be played as a phase . Would I play those 3 notes using one bow action? How do I choose what notes get a full bow and what string of notes get a full bow?

I depends on a number of things.

1) Tempo- It is impossible to fit a lot of notes in one bow at a slow tempo, but it's easier than doing them separately at a fast tempo.

2) Volume- If it's loud, you can play things loudest in separate bows, because you can use more. Obviously, the inverse is also true: playing things quietly require less bow and can be easily slurred together.

3) Time Signature- this sounds kind of weird, but true. In general, players try to play the first beat of each measure down bow (an exception might be 3/4 time, which might be easier to do bowing "as it comes," which means it's always down up down up...) So people often slur things in such a way that will allow this.

4)Articulation- If you want it smooth, then you might want to consider slurring it (you might want two or four or however many notes in a bow, depending on many of these things). If you want it more detatched, then separate (but you can still make things sound smooth, even with separate bows). Accents often call for separate bows, and are sometimes all down bows, with retakes in between.

5) Style- Of you know what you're playing should sound like, you might get a better idea of this. Every composer and time period has a unique sound, best approached with different bowing styles.

6) What did the composer write?- Sometimes they don't write anything. Sometimes they are just going for the general sound they want, and write in impossible slurs. Any articulations they write will be a clue to what you should do, but you might have to modify it to make it practical. You should be more inclined to obey any bowings from a string-playing composer than one who played piano.


So, with all this, you might be more confused! I don't blame you! This just sums up how complicated bowing can be. This is also why you'll get different editors of the same piece, all with something entirely different. In an orchestra, it is completely normal for a section leader to put in whatever bowings they want, which will be entirely different than what a different person would put in. It's normal for me to have bownings in the music, then have my teacher change it, then I'll change it, then I'll do a masterclass and THAT teacher will change it, and there's a good chance me or my original teacher would change it back. THERE IS NO RIGHT ANSWER. Sometimes, there are wrong ones, but if you can do it, it should be all right.

My advice, then, is to try it both ways and see what you like better. You could find different editions of the same piece, and you'll see recommended bowings by different people, and you can pick parts of each that you like. Bottom line is to do whoat you like better. You might like the sound of one better, or maybe one is easier, and both are valid reasons to pick whether it's separate or slurred.

Have fun!

Thank you for your answer. It was very helpful