I wasn't able to find much information on this for classical (and soundtrack and everything else for that matter).

I would just send them the final mix as an uncompressed 32 bit float file
and leave the final decisions about peak level and compression/limiting to them. Leaving them more room to adjust allows them more options to achieve the best end result.

I try to leave between 6 and 18 dB free on the top for them to play with. I won't compress the 2-buss at all or the main pair but I might occasionally compress spot mikes to help hide them. LUFS will vary all over the place because that's just how it goes when you have a lot of dynamics.
--scott

if i'm not mastering myself, i don't aim anywhere other than not getting any clipping or distortion during production.

if i'm mastering myself (for cd/dvd release), i hardly ever go higher than -18dB lufs for classical music; peak (assuming there is no isp) is mostly -0.3dBfs.

mastering for broadcasting is another topic, as well as for playback on pa systems or for backing tracks - and i'm not yet even talking about streaming or vinyl...

short: times for a single master that does it all imo are long gone!

Avg LUFS at -18dB, reserve peaks at -2 or -3dB if going for external mastering, peaks at -1dB for my mastering efforts,

Jnorman. How do you get -1 peaks without using a compressor? Unless you mean for the actual master, right?

Not for anything recorded?

For capture, I never like seeing the absolute loudest thing on the recording go over -6 and I keep my averages at around -18.

D.

Doug - no, recording peaks are kept at -12dB or so. I use “purestgain” plugin from airwindows on the master buss to adjust LUFs. Though I do often use pro-c for very mild compression at times (it has a pretty smooth preset called “tighten classical music”), but I don’t use compression to add gain.

I think you should ask the mastering engineer for her or his preferences. Some of them post their desired specs on their website, but if not just send the engineer an email and ask. It'll save you both some time.

The mastering engineer I worked with on our most recent project simply told me to keep true peaks below -3dBFS; no guidance at all on LUFS.

A lot of studios have this information right beside the service description.
I would look at the webpage or just ask the engineer directly.

This is usually what I aim for.