In an attempt to get optimum levels and pre tape eq settings, and to gauge 'tape saturation levels' try this...
Have the musician(s to) play without headphones, (and not in the control room with you) then hit record, but with the recorder into "repro" mode. (not the usual "sync" mode)
There will be a very big time lag to the audio coming out of the recorder as it plays back from the record head instead of the usual sync head. (you might not be able to do this with
all tape machines, but most 2" machines will allow this..)
in this mode you can
1) Push levels to tape to find the 'sweet spot' for saturation
2) EQ signals going in so they come off the tape machine sounding the way you want then to sound.
3) Give band members a laugh.. (for some reason ALL musicians find it totally HILARIOUS to watch their drummers arms flailing about out of time with the playback audio..)
I used to use this technique in studios with worn tape heads / dodgey tape machines..Especially with drum kits / basic tracking because at least I knew what I would be getting on playback..
Of course there is a short time lag in your eq actions and your fader movements due to using the repro head but once you get used to it, you are good to go,
Recommended.. seriously..
(warning - obviously you are running in record to get the sounds set up, so you need a blank reel to work on, do not go rolling into the next song in record! Cause you will wipe sh!t out!)