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The 85% Rule: How to Play Pieces Perfectly Polished at Full Speed


How can we know when a piece of music is “ready”? How do we know when to call it “finished”? How polished is polished enough?

At what point can we trust that the piece will be there when we need it? If we sit down to play, will the music flow?

The “85% Rule” gives us a concrete metric we can use to gauge readiness.

The Challenge: Musical Perfection at Full Speed, Every Time

Someone said of actors: An amateur practices until they remember their lines. A professional practices until they can’t forget them.

In music, as in acting, the performance happens in the moment. It’s ethereal. We create fleeting moments of art using sound. It’s there, then it’s gone.

And because we’re human, mistakes are possible. We need focus and attention in every moment. Each note has its challenges. And our job is to render them, perfectly played, at the exact right moment.

Accuracy and Precision

Music happens one note at a time. And for each note, our fingers have to move in specific and precise ways.

Our hands have to synchronize perfectly. We have to use just the right amount of pressure and speed.

For even a short piece of music, there may be hundreds of small details. Music demands an ornate choreography, made of extremely small movements and variations.

Musical Expression

And all the movements serve a higher goal. Each movement, each pressure, each velocity seeks to create an intentional sound.

Each piece of music has an emotional core – it has something emotional to say. And we try to communicate this emotion using our fingers.

To do this, we use volume (dynamics), rhythm, and tone. We attempt to breathe life into the black dots on the page.

It’s a tall demand – to play each note accurately. Especially at precisely the right time, with the perfect tone quality and volume.

The Random Error or Memory Slip

So it’s no wonder we make mistakes. With all we try to do, it’s no surprise we often slip and mis-finger something.

As we track the volume, tone and everything else, we may become distracted and lose our place in the music. We may forget some note or detail, especially at top speed.

So how can we prepare? How can we feel confident about meeting all these challenges?

Two Separate Elements: Knowledge and Ability

We can think of playing a polished piece of music as two separate abilities. One involves the mind, the other the body.

(This is a false dichotemy, but a useful framework.)

Knowledge of the Piece

First, we have our knowledge of the piece. On a large scale, this means the title, composer, tempo (speed), the time period in which it was written. We know the style, the mood, the attitude.

Zooming in, we know which chords make up the left-hand fingering. We know the right-hand fingerings for each note.

We’ve made decisions about which notes get louder, and which get quieter. We’ve decided which notes pop out and which stay in the background.

Some notes are melody, others are the bass. We know the role of each note in the piece.

This is the study of the music. It’s anything and everything we know, think or suspect.

(As we mature as musicians, our knowledge becomes richer and more detailed. We have more experience and context for each moment in our pieces. This is one of the joys of long study.)

Technical Ability

Apart from everything we know about the piece, we have our ability to execute.

Each musical moment, each note, has specific technical demands. And we are more or less able and equipped to meet those demands.

For a given piece, we may need to use right-hand alternation at a certain speed on the metronome. We may need to shift the left hand and land on an awkward chord.

For everything we know needs to happen, our body is able (or not) to do what needs to be done. And it has to do this at or above the speed needed for the piece at hand.

The 85% Rule

Enter the 85% Rule. This rule says that if we can play perfectly at 85% of the performance speed, full speed will be fine.

This assumes we have the physical abilities to play at full speed.

The goal is to play through the entire piece at 85% of performance tempo. Start to finish, with all musical decisions, inflections and expression.

And here’s the important part: no mistakes allowed. Clean and flawless, like stainless steel.

If we can do this consistently, performance at full speed will be a success. The extra speed will not compromise much.

And while we can’t guarantee that we’ll play with no mistakes, we will feel confident and prepared.

This way, we can release any worry, and just enjoy the ride.

Note: Depending on the performance tempo (speed) of any given piece, we may find that 75%, or 90% is more appropriate. The principle still holds: well-polished below tempo means more chance of success at speed.

Slow Practice Takes the Prize

The 85% Rule takes advantage of slow practice. Slow practice has many benefits.

Speed creates the illusion of perfection. Slow practice shows us a more realistic version of how we play.

As they say, “Speed kills, awareness cures.”

Correct repetitions

The more correct repetitions we make in our practice, the more likely we are to play correctly on cue. We train ourselves to play with polished clarity.

Conversely, the more mistakes we make, the more likely we are to make mistakes when it counts.

Slow practice gives us the time to play intentionally, and make correct repetitions.

Well-trained focus and mental stamina

Slow practice demands focused awareness. If our minds wander, the music falls apart. So we train the habit of paying attention. And this contributes to better performances.

Appropriate physical tension

First, when we slow down, we negate our muscle-memory. This means that we have to use our other faculties, and truly know the music.

And it also lets us meet each moment with more appropriate tension.

At full speed, we often use more effort than needed. Slowing down lets us train appropriate tension and release into the choreography of the piece. This is part of the polishing process.

Warning: It’s More Work Than You Think

The concept of the 85% Rule is simple. This one of the reasons it’s so useful.

But in practice, it’s not so easy to play perfectly polished music, even below full tempo.

And the more phrasing and expression we bring to the music, the harder it is to play without mistakes. It takes more emotional, intellectual and visceral “bandwidth” than simply playing the notes.

But if we do the work, and put in the focus and time, the 85% Rule offers a concrete metric we can rely on. We can feel more confident, and perform at higher levels.


Allen Mathews

Hi, I’m Allen Mathews. 


I started as a folk guitarist, then fell in love with classical guitar in my 20’s. Despite a lot of practice and schooling, I still couldn’t get my music to flow well. I struggled with excess tension. My music sounded forced. And my hands and body were often sore. I got frustrated, and couldn’t see the way forward. Then, over the next decade, I studied with two stellar teachers – one focused on the technical, and one on the musical (he was a concert pianist). In time, I came to discover a new set of formulas and movements. These brought new life and vitality to my practice. Now I help guitarists find more comfort and flow in their music, so they play more beautifully. Click here for a sample formula.





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