I consider myself an advanced classical pianist, being able to play many Etudes, Ballades and Sonatas by Beethoven, Liszt and Chopin, for example. However, I have been struggling to play pop music for over a year now; I don't know how to play pop piano properly. I sometimes think that it's actually different on a very fundamental level. FYI, for pop music, I mostly improvise melodies or play as an accompaniment.
I'm in a similar situation. I was classically trained for 13 years, and 6-7 years ago I started playing pop styles. I'm still not excellent at it, but I've come a long way and am generally competent.
The biggest difference, as I'm sure you've discovered, is that you can't just play what's on the page (if there even is a page!) and have that be enough, which is pretty much all you ever do with classical. Instead, all of the interesting stuff comes from what you do with it. The chord progressions are simple, repetitive, and boring on their own, you have to do something to spice it up.
Study as many different pop pianists as you can, and focus on how they voice chords, the gestures they use to fill the bar, and how the bass moves. Many of the patterns look very similar to classical ones, but with different rhythm and accent patterns.
A few bands/artists just to get started with:
- Billy Joel
- Elton John
- Ben Folds
- Nick Cave
- Jason Robert Brown
Regarding that last entry--Jason Robert Brown is a contemporary musical theater composer who isn't well known outside of musical theater enthusiasts. However, he's an excellent pianist with very intricate parts, and much of his music is available to purchase fully notated as he plays it, so it's a good one to study.
This is all great advice, but it treats you like a total beginner who doesn't know what to do. You have a huge advantage from your classical training, which is the ability to read. I would look for the most detailed transcriptions of the type of pop music you want to play -- for instance, if you like the Beatles, see the Complete Transcriptions which capture everything on the records, note for note. The point is, of course, to be able to play by ear -- but you can jump-start the process by listening to excellent players while following along.
A great place to learn how African-American groove music works is in boogie-woogie piano music, a lot of which exists in detailed transcription. Check out "Honky Tonk Train Blues" or anything by Pinetop Smith, Meade Lux Lewis, Albert Ammons, etc. You'll immediately see how the hemiolas and cross-rhythms work, and start to feel the polyrhythms in your hands.
I'm not an advanced pianist by any means, but one difference I've noticed is that classical music is more voice-oriented than pop music. That is, it concerns itself largely with horizontal relations between notes to create multiple independent melody lines, each following voice leading. In pop music, these seem to be much less important relative to the vertical chord relations. I had to stop thinking so much about voice leading, and just start playing chords. In my case, as bizarre as it may sound, learning to play a simple chord-based accompaniment on ukulele helped me to do that.
Another big difference is the rhythm, and the prevalence of African-rooted syncopations. For example, many pop styles don't break a 4/4 bar into two or four equal groups, but into 3 unequal groups, such as 3/8 + 3/8 + 2/8. In some styles, melody notes will very often avoid playing on main beats -- think of ragtime, for example, which is sort of a bridge between classical and jazz. To some extant, rhythm has to eventually come by feeling it. But in my case, I often will have to work it out by detailed, slow-motion counting before I can get to that point. Syncopated rhythms are one of my weaker areas.
In terms of harmony, simple pop music often uses relatively simple chord progressions (I-V-vi-IV and I-vi-IV-V will get you halfway there). But some more modal blues-based styles will focus on subdominant chords, and flat chords (rather than Classical's dominants). So you might see things like I-bIII-bVII-IV-I. More jazz-based styles will have their own harmonic language including elaborate chord substitutions and extensive use of sevenths, ninths, and more extended variants.
When improvising melodies, you might start out limiting yourself to a pentatonic scale, since its the "common denominator" between tonal and modal harmony. You might also try using a blues scale.
Something that makes your question difficult to answer is that you talk of "pop music" as if it's one genre. In fact if you pick two pop keyboard parts at random, you're likely to find that they're using completely different techniques.
One pop song might be backed by long chords of synth strings. Another might have a showboating solo on a monophonic synth. Another might have a boogie-woogie-like piano rhythm.
You need to listen to the kind of pop you want to be like, and decide which techniques you want to learn. One instructive exercise would be to listen to a piece of 80s synth pop, for example Yazoo or Erasure, and see how many parts you can pick out and play.
In a lot of band situations, the ability to create an accompaniment from a chord sheet is important. So learn how to shift a piano roll between chords. You can even do this with bars from classical pieces you already know.
For soloing, getting scales etched into your brain is the key. You already practice major and minor scales; for soloing you want blues and jazz scales. Any book on jazz piano will introduce these scales early on.
Pop music is very different indeed. (Fill in black music/white music stereotype here.)
Things usually done wrong by classical players:
- In the beginning, there was groove. If everything else fails, the groove must survive! You can't play the wrong note, only at the wrong time. Don't relax, keep the tension. There's a trap door under your chair: lose the groove and you're off the stage. Don't try, be on fire. Be an animal. Be on 10,000 volts. Blah, blah. Oh, did I tell you how important the groove is?
(Large gap here)
- Keep the same tempo throughout a song, in every bar, in every note. Even if it's the only note in the whole bar. For a pop musician even a Bach prelude is considered rubato ;-)
- In Pop/Rock: legato quarters, staccato eights. In Jazz: non-legato quarters, legato eights.
- Your staccato is not short enough.
- Accentuation on backbeat: 2, 4. Not 1, 3. It's really not a march.
- There are syncopations in pop music. No, those in classical music are not.
- In Pop/Rock: Eights have accents on the beat. In Jazz: off the beat. Non-accentuated eights almost inaudible. The hotter the music, the muter these notes.
- Pedal down after the note. Nobody cares about overtones!
- You play too many notes in your improvisation. You don't have enough rests in your improvisation.
If lessons are an option for you, there are instructors that teach pop styles - I'm currently doing this with my instructor. We work out of books that explain the rhythmic / melodic etc. ideas that make, for example, blues sound like blues and rock sound like rock. Good books explain the theory behind what's going on, and have plenty of dots if you're comfortable with that. They'll also come with a CD so you can listen and / or play along.
I’m not a good pianist, but I did spend my entire childhood learning the way of classical pieces. I started to play pop music (basically Christian pop songs) in my church, and it is indeed a similar but different kind of music.
It took 2–3 years for me to start getting the hang of pop music (again, I’m not a good pianist). As others have said, the first thing you should do is leave the paper and start to rely on your ear.
Classical chords (especially on the advanced pieces) can be used to amazing effect in pop music; you just have to analyze which chords serve best in which circumstances. Also, try listen to Korean and Japanese OSTs: they have some real good improvisations on the melody and chord progressions (if you’re playing romantic pop music). Once you’ve understood the general patterns (which won’t be too hard since your fingers are well built for heavy training), try something new, like adding jazz / blues / etc. into the music and take if from there to other unexplored areas.
Oh yeah, the most important thing that divides good and not so good players in pop music is knowing when to hold back and let the others take the lead; IMHO this contrasts with classical music where the piano is always at the center.