Another interesting question about tremolo is the right hand finger combination. Which combination or pattern is the best? The most commonly used pattern, mentioned previously in my tips about tremolo, is p-a-m-i. It is the one I have persevered with for many years and has served me well. However, there are other patterns that can work just as well if not better.
Some of the best players in the world, such as Ana Vidovic, use two-finger tremolo. The patterns p-m-i-m and p-i-m-i both exclude the a finger and have the advantage of being capable of producing an even tremolo effect. Sometimes and for some people the a finger can make the tremolo uneven. On the other hand, some players might feel that it is too much work for the i and m fingers alone. Including the a finger means that the effort is shared between all three fingers.
Flamenco guitarists sometimes take things a step further by using a four finger tremolo pattern. That is to say, for example, they might play the thumb followed by four fingers, i.e. p-m-a-m-i. That's actually three fingers with the m (middle) finger used twice. A guitarist with phenomenal technique might make this work at speed but there is the danger of the effect sounding laboured, as if the guitarist is struggling. If the tempo is slow, then the four note tremolo can be quite effective and achievable.
Most players just want an even tremolo that is not going to be an unrealistic struggle to produce. Ultimately the choice comes down to each player’s preference and what is physically possible due to right hand finger posture. If you have a standard right hand technique then the p-a-m-i pattern should be possible. However, players that have a right hand position like that of a lutenist, with the thumb positioned inside the fingers, will most probably find a simpler, two-fingered pattern more suitable. There may be other factors such as relative finger lengths that also affect the choice of pattern.