I like the tempo and pacing. It was nice to hear someone treat this piece as if it is somber, elegant, and thoughtful.
The recording was difficult to listen too. I downloaded it and boosted the levels by 24dB.
I'd say that you should work towards using the manual input level controls on the DR07 and you can safely boost them 18dB over what you had set for this recording.
The noise floor from the HVAC was very high, meaning that the signal to noise ratio was very low and I could hear that the mics in the Tascam captured a resonant peak in the mid range.
I would consider the placement of the DR07 and make sure that it is secure so that it's light weight body does not resonate and add to the peaking in the mid range... where was it?
Are you playing a upright or a small grand? Do you have access to the sound board?
In general, you want to get close to the sound board to minimize the room noise... but you need to balance that against a desire to capture some sense of the room tone. If you get too close to the soundboard the recording will sound unnatural and sterile. So, work on getting more piano, less noise, but keep some room in it. Try to turn of the HVAC when possible. ( I work in a lot of remote locations where it is not possible... so try but if you can't just keep making music )
One of the marvelous things about your recording is that it does have lots of room tone in it and this makes it seem very natural and pleasing.
I have a DR05, it has a small mounting screw hole. I imagine the DR07 does as well. Get some adapter hardware and mount it to a mic stand so that you may place the mic where you want. Don't let the for factor of the DR07 prevent you from getting the mics where they need to be.
FWIW, I did a level boost and a couple passes of noise reduction passes on your mp3 and it is much easier to hear your nice playing. If you PM an email address I'll send it to you and you can consider uploading that to SoundCloud.
Thanks for sharing.
best regards,
mike