Low volume listening dynamics

and......of course......there is always the ’sit closer’ idea for times when you want more immersion at lower SPL’s.

it does allow for less ’room’ and more ’direct signal’......so the energy does not dissipate as much.

i’m in the near-field all the time anyway. but my room is ’super-tuned’ to be balanced at ’warp-9’ even when i’m in the near field. took many years of work to do that. room reflective glare drove me back until i figured it out. but at low volumes that reflective glare is much less. so it’s a quick and easy (and free) thing to try.

might need to adjust toe in for tonal balance and imaging for sitting closer.....but the advantages might be worth it even if those are slightly compromised if it's occasional.

I plan on getting a new Luxman integrated amp soon and one of the things I like about the Luxman is that it has a loudness button on the remote. My old Denon integrated amp from the 80s had a loudness button as well. Not sure why newer amps don't have a loudness button---it's definitely good for lower listening levels.

A little expansion on some points others have made.
Higher efficiency speakers may help, amp cleaner and faster at low power may help, and room and distance can also help. Clean fast response of both Amp and speakers with minimum ringing and resonance are what can make music sound musical regardless of efficiency and power. There are low efficiency speakers that combined with the proper amp can be more musical than high efficiency speakers with any amp. Remember that speaker efficiency is just a measure of sound pressure at a reference frequency at a reference power level. It really doesn't say much about how musical the speaker is. It is only really helpful when trying to match multiple speakers in surround applications to try to even the response.  Waterfall charts can help you find speakers that you may find more musical to you regardless of efficiency, and they will likely sound more musical regardless of the volume level.

My own observations and experience are that you need close to 20 db range above ambient noise level for music to start becoming musical. 30-40db starts to get real. Below that you can tell it is music, but nothing you do will make it musical as in detail, depth, soundstage and revealing. Loudness compensation does little to change that, just helps hear some frequencies that are masked by the background.

So the real questions are what is your background noise level, and what level above that do you consider low volume.

I am in an apartment and have a bg noise level of 40-45dbA at the minimum. It can commonly be 50-55dbA with appliances and fans running in my apartment and adjoining ones. In my main listening area with minimum bg noise level, volume at 65dbA peak begins to sound musical and gets better up to 85-90dbA. Above that room reflections and reactions start to counter any increased musicality.
In another room I have a work station and a near field setup. With computer and drives running the bg level is higher on average, but since I am near field, 20 dbA above ambient is not only fairly musical, but has some depth and height, no sub or loudness control needed.

YAMMV

All the answers are here...low ambient noise, good 1st Watt, effective tone controls for shaping the source to sound balanced at your listening level, and controlling the room's reflectivity around the speakers.  I disagree about needing high sensitivity speakers entirely.  I would say a bigger factor is to have speakers that are not lacking in bass extension, b/c at low volumes, that exacerbates the lack.  I agree with Erik in recommending looking at Yamaha...if the model has their variable loudness, like the AS701 or AS801.  Interestingly, their new higher end models drop that feature...although they do have bass and treble controls (with unspecified characteristics).  I have a vintage McIntosh C20 that has a fantastic variable loudness control that really works well.

Mike, sitting closer is just turning up the volume. It certainly helps negating any room problems.
The beauty of having 8 foot line source dipole speakers is that you are always near field even 12 feet away. 
Irregardless of the equipment being used and the room are in you can not magically overcome the Fletcher-Munson effect. Bass and treble have to be boosted to match the volume level or you will be missing low bass and detail. 
The only way to overcome this without an advanced digital system is to adjust the volume until things sound right and there is not a single level. It depends on the way the recording was mastered. Some records don't sound right at lower levels others hurt if you play them too loud. 
This is for serious listening. For background music it really does not matter.