Using timing to scroll eliminates the ability for the player to add any speed variations in a piece, which most experienced players would.

It's a fun app for the common folk, but useless to experienced players.

I don't think that's the deal breaker for experienced players. That'd be pretty to solve with a bluetooth foot-pedal. Here are a few of the things that come to mind that pro-level folks would have hang-ups on:

• Typesetting: I don't know what score format they're using, but this can be a big one. There's a big difference between a professionally engraved score and just having the right notes there.

• Annotations: From the conductor, self, whoever.

• Overview: Professionals scan a score looking for key parts. This seems virtually impossible in iPhone format, but would be workable on the iPad.

• Size: Even the iPad is small compared to a performance sheet music page.

I suspect the three big market segments are hobbyists, children and church musicians. There are relatively few professional performers.

It was mentioned elsewhere that the typesetting is done via LilyPond, which is supposed to be excellent.

Just like tex the quality has potential to the very good, but when you stray from the defaults it suddenly takes a lot of tweaking to produce a nice-looking score.

Some really basic audio recognition should enable the software to figure out the current position on the sheet, hence making it useful for experienced players as well.

Do this. Would also be useful for beginners who make mistakes and often need to repeat portions.

really basic? score following is hard.

The audio recognition bit is indeed basic - all you need to figure out is the note and possibly the length of the note.

The following part hard is a bit harder, but not impossible - compare what you have recognized with what you was expecting. If it's not what you expected, look around the last known position and see if you can find the pattern you recognized (while taking repeat signs etc. into consideration).

you don't have to follow it in perfect-realtime, you could totally mimic a human page-turner who flips the page at about the right time.

Nah, not useless -- come on. The speed variations aren't going to be that huge, and the variations will matter even less on an iPad. I can imagine a number of technical solutions to this issue that don't involve any signal processing. It's a valid point insofar as it would need to be addressed for advanced players, but let's not be so quick to dismiss this guy: the app is absolutely beautiful and he's clearly skilled and thoughtful.

I wasn't dismissing it. For 90% of people who would consider this app, it's great! I really just posted this because someone previously said that this could replace sheet music.

The highlighting of the keys is also an amazing feature. I've posted YouTube videos of me playing the piano with the camera angled unintentionally over my shoulder.. and actually used the video to see what keys I was playing and copied what I was doing.

There should definitely be a "no sheetmusic" mode in this app for people who previously copied people's finger position on youtube... for people who have no desire to learn how to read sheet music.

Good luck.

He's not dismissing it, he's giving feedback. This is exactly the kind of thing I'd want to hear if I were launching - how I can make my product better and appeal to more people.