FlyingKebab wrote:
Technically you can get 100% accuracy without listening to the music much (although this isn't what you should do in a rhythm game). Each song has a BPM and is chopped into beat parts or so to speak. Each attack rate has a set delay before you have to hit the circle to get a perfect 300. Each beat should technically be spaced equally apart 1/1 1/2 1/4 1/8 1/16 in a 4/4 or similar layout. If you hit the first 300 on spot which you can do by knowing the exact delay of the attack rate then if you don't fluctuate on speed you will get all 300's on that particular beat part. Then you use the Attack rate delay on the next beat part and get all 300's and so on. It's like thelewa said: you have to have to follow a 1/4 grid in your head. Although just listening to the music instead of caring about the attack rate is generally a lot easier and less stressful/technical but it does require you to have good rhythmical skills.
You still need the music. To say it's "possible to play without music" is just to explain the principle behind this technique. It's the same principle as having a mental offset. The music also gives you plenty of clues for upcoming patterns.
- Visual:
You see notes, you know that delays must be compensated for in some way, either due to the music's offset, adjusting for your own delay, or your keyboard delay etc., but everyone knows when they should hit the note from a visual cue. It may feel or even look earlier than it should be, but it works and that's how you initially learn the game. A lot of people get this feeling and that's why they don't focus on approach circles much.
- Audio:
The music dictates the timing intervals (BPM), but you can't keep listening to the music as a consistent metronome reference, since sometimes it goes quiet, changes ticks, involves more/less instruments etc... it changes... it's music.
- The middle-man to bridge them:
So you determine the exact timing interval from the music and develop your own internal metronome from it (may not even be perfectly synchronous because of offsets), which you maintain consistently at all times, referencing only the most distinguishable beats in the music to keep that timing consistent, and apply that to your personal visual cue.
The end result is: You're paying attention to something in-between audio and visual, instead of one or the other. That's why it's called a "mental offset", to compensate for errors on both sides of your interpretation of the music and beatmap, or errors intrinsic to the beatmap itself. That's also why it's possible to play the game accurately even with an incorrect UO.