I'm just downloading some files I need for the session so I'll add a couple of things...
I mentioned 'nail clicking' a couple of times. Your potential client also said your test recordings sounded too close. For classical music on a classical guitar, a lot of the attack of the sound produced is very undesirable, which is why close mic'ing is generally a terrible idea in this context. It's not just the nail clicking that's the problem - the usual string squeeks, breathing, chair creeks, the sound of the skin in the right hand fingers passing over the string as it moves onto the nail - everything just sounds too close.
It's an important concept to grasp when recording classical music - virtually all of the advice you read online and in magazines is intended for recording of popular music which calls for a completely different technique. Indeed, when recording pop music, we can use some of these characteristics, which were problems in our classical recording, to our advantage. The exaggerated attack portion of the sound can help a nylon string guitar cut through a mix, the sound of the skin on strings can yield a very intimate sound which can enhance a song etc. The key is
context. Same thing applies for other instruments - close mic'ing a violin might give great attack and grit for a pop song, but try close mic'ing a classical violinist, and watch how hard he pokes you in the eye with his bow!
Try and understand
why we do certain things when recording, and you'll become a much better engineer (I hope I don't sound condescending, like I'm a great engineer - I'm not! No Grammys for me!). Why would we want to close mic an instrument in the first place? To achieve better isolation when recording in an ensemble, to increase the source to reflections ratio, to use the exaggerated attack to compliment/enhance the style/mood of the song, to enable an instrument to cut through a mix better, to increase the lows by utilizing the proximity effect, to 'spotlight' a certain frequency spectrum, enabling the instrument to sit better in the mix, and I'm sure there are more reasons that I can't think of right now. But almost none of those reasons apply to classical music.
The point I'm trying to make, is don't do things 'just because'! If you understand
why you're advised to do certain things, you'll be much more versatile.
As an example of all of this, listen to an album John Williams did in 1978 entitled,
John Williams Plays Manuel Ponce. It sounds terrible! The producer of the album (Roy Emmerson) obviously wanted to experiment with studio recordings, and close mic'd the guitar in a totally dead studio. Now John Williams was almost certainly the most accomplished classical guitarist in the world at that time - he is an exceptionally clean player, and technically flawless, so if anyone could pull it off, he was the one - and yet the recording reveals things which just shouldn't be there, and the listener feels very uncomfortable listening to it. Even though that sound is used every day in popular music, it just doesn't work for classical music. Why? I don't know, it's an interesting topic - is our perception of what classical music should sound like a social/cultural construct, or an acoustic imperative? PhD topic anyone?...
I'll end with a question for our technical gurus (are you out there bitflipper?!). Why does close mic'ing exponentially exaggerate 'noise' like nails clicking the closer you move the mic? Is it that those sounds disperse faster, are room reflections the key factor, 'spotlighting'?