The Basics of Nail Shape
What really sets classical guitar aside from other forms of guitar is that the way you shape your nails can have a great effect on how you play the guitar and how you play certain strokes. The first obvious point which is the same for all guitars is that your left hand should have short fingernails, ideally as short as you can go without causing pain. This allows you to get the fingers of your fretting hand onto the frets at about 90 degrees which gives you the best fretting angle and produces the best sound from the string. A beginner guitarist will struggle to get their fingers at 90 degrees to the fretboard and it can take quite a bit of practice to perfect it. Initially most beginner guitarists will accidentally mute the strings below the string you’re trying to play, often meaning you can’t play the notes you are after and creating a dull muted sound. If you do not have short fingernails on your left hand the nail will touch the fretboard before the flesh of your finger making it impossible to get a good sound.
The nails on your right hand however should generally be grown longer. You should file the nails of your right hand to have a slight angle to allow your nail to slide across the string creating the sound just as your fingernail leaves the string. This allows higher volume and allows you to accentuate certain notes to define your melody. The smoothest sound is achieved by keeping ensuring that the flesh of your fingertip touches the string very slightly before the nail touches the string. This will allow the nail to slide off the string to provide a nice round sound without catching your nail. In general the nail shouldn’t be too long and should just be seen over the fingertip when looking at the palm of your hand. If it’s much longer than this the nails will tend to catch on the strings.
Keep Them Smooth
An important point is to ensure that when you are filing your nails you finish them off with fine sandpaper or a fine nail file to make sure the nails are smooth. If left rough you will often get a scratchy and uneven sound as you play.
Nail shape is a real sticking point for many guitarists and I have had problems with this myself over the years. The angle of your nails needs to match your playing style or your nails can catch on the strings making it difficult to play. There is no real correct angle for your nails so when you start playing you will have a bit of trial and error to get it right. Your nail angle is a very personal choice, Francisco Tarrega for instance had very short finger nails on his right hand whereas Julian Bream or John Williams have longer shaped nails on their right hands. I’ve included a photo of my nail shape for guidance. The nails are also used to tap the body of the guitar if you are playing flamenco.