How many different volumes can you achieve with one note? There are many expression markings for volume from ppp to ff and sfz. The full range would go something like ppp pp p mp mf f ff fff sfz. That’s a staggering nine differences of volume. Can you achieve that by choosing one note say a B on the A string and achieving an audible difference for the listener of nine discernible changes in volume from your quietest whisper to your loudest down stroke? Can you then achieve the same thing with tremolo? If you find that difficult its not surprising because plucked string instruments are not renowned for their range of expression.
A good place to start is to take just four different volumes p mp mf and f. Start with playing your quietest p, then for your loudest ƒ. Alternate between these two playing four notes of each. Can you be consistent are all the ps the same and are all the fs the same. When you have control of these then you are listening for two more divisions. One a bit louder then p and one a bit softer then f. Practice going from p to mp and back. Again four notes each. Do the same from f to mf. Now play through, four notes of each, from p to mp to mf and f and back again. Is there a difference between mp and mf? When you have practised this with down strokes then do the same with tremolo. Ask a friend, partner or fellow musician to listen to you play then sound them out to see if they can tell you when have changed from one volume to another.
When you have achievedfour you can experiment with ever more subtle variations in volume. Can you make your quietest even quieter and can you make your loudest even louder? Does it make a difference where you strike the string in relation to the sound hole or f hole?
If you want to spend some enjoyable practice time working on expression I highly recommend Alison Stephens’ book ‘Six Episodes’ as a starting point. The first piece ‘Reflections’ demands a range from f to ppp. It looks deceptively simple on the page and its true value as are all the pieces in the book is to encourage a full range of expression and precision from the player. Her books can be bought from www.astute-music.com.