Discrete v/s Continuum Instruments

Disclaimer: Anything I write below comes from the past six years of my self-training in music. I have never had formal music education. I have almost zero experience with percussion.

I divide all non-percussive instruments into two broad categories: Discrete and Continuum.

Discrete instruments have clear markings for the natural notes. For example, a guitar is a discrete instrument. It has fret markings at varying distances where the notes ring out. The flute is also discrete. It has holes that let air pass through and produce the notes. The piano is fully discrete in the sense that it is impossible to play anything other than discrete notes on it. The easy part of learning to play a discrete instrument is being able to play the natural notes. However, the difficult part is being able to play bent notes. The seven notes of a musical scale sound great to human ears, but they can become monotonous to listeners. It's the ability to distort those notes through bends that adds feeling and emotion to playing. There are many forms of bends: a quarter bend goes a quarter step up or down, a semi-bend goes a half step up or down, a vibrato bends the note up and down rapidly, centering around the note, and a slide can temporarily cover all the frequencies between two notes in rapid succession. Bends are difficult on discrete instruments. For example, on a harmonica, it requires special tongue action to direct the air in a way that produces a bent note. A piano cannot play bent notes unless it has a pitch bender pedal.

On the other hand, continuum instruments don't have markings for the natural notes. The notes need to be found purely by practice. For example, the violin (and other instruments in the string family) is necessarily a fretless instrument. It can take an insane amount of practice to be able to place one's fingers at the exact points where the natural notes ring out. The continuum fingerboard is another such digital instrument. However, once you can find the location of the notes, both natural and bent notes will take almost the same amount of effort.

From my experience, every musician should learn at least one discrete and one continuum instrument. A discrete instrument will help you quickly land on the natural notes but will require a lot of practice to bend them to get the feel right. This will help you master the bent notes. On the other hand, a continuum instrument requires putting in a lot of effort to get the natural notes right, as you will almost always hit higher or lower than the actual notes. This will help you master the natural notes.

I do not have any recommendations for a specific discrete instrument, but I do have one for a continuum instrument: the voice. Vocals are a continuum instrument. From my experience, I can say that the voice is the highest form of continuum a musician can ask for. Violins have a clamp at the beginning of the fingerboard. On a tuned violin, you can always play the open string to figure out at least one note, and then your relative pitch can help you find the others. The voice has no such clamp. In solo singing, once you lose track of your root, you are completely lost. There is no way to get back to the root.

I would recommend that every musician learn vocals, no matter what other instruments they play. I saw a huge improvement in my guitar playing after I started learning vocals. Vocals will help you master relative pitch much faster. They also improve other aspects of musicianship—perfection and feel.