The slower the tempo, the harder to make melodic line flow, so I'd bring it to speed, first. Then it will be much easier.
Best, M
Really? I can't say the idea is wrong but I feel it takes phenomenal experience and voicing skill to make onward motion an early priority. For me, slow free time is the way to learn to relate sounds. The fact that melodies easily sag in slow tempo is what makes this practise so valuable. You have both the time to listen in to every sound and the chance to really observe whether the melody carries, in a situation where failures are most easily detected by the ear. If you make notes sound long and sonorous in a leisurely free tempo (with neither dips in sustain nor hard attacks, you can begin to worry about moving along. If it doesn't sustain already in casual tempo, I wouldn't put a trace of pressure on. From teaching some very good students in chopins c minor nocturnei, I always find any tempo pressure kills voicing in the middle section. Only by eliminating time pressures do i find they listen in properly to whether the melody can sing as a truly different level over background harmony. If they don't make room to hear every step of the spread and make extremely long melody notes float on top and last out (without any urgency in the spread) I find its almost impossible to get students to listen in and match up lasting tones. Until the melody can float separately from the other notes as if as if to last forever, I find that any sense of pressurisation kills voicing and sustain. An advanced pianist may skip that step, but if it's not assured that they are already capable of floating melody notes to the next (with as many as three or four seconds of audible melodic sustain) I wouldn't generally expect them to have success at sustaining a long line under tempo pressures. In these passages, I always think of the sound of artists like richter at his best or nyiregyhazi. Only when the melody can float across seemingly endlessly (without interruptions or drooping) do I start to encourage any sense of pressure to move forwards. If a melody can carry at half tempo or less, the pianist really understands voicing. I'd always aim for that first, under as little pressure as possible to do anything other than listen to balance of the melody, before even considering the next spread. Carrying from note to note is easy in a more fluid tempo, but it's also harder to avoid lumps and to sculpt every note. Slow sustain is a superb challenge in itself and the beginning of being able to put onward pressures on while keeping true tonal control. When every note is controlled slowly first, uncontrolled surges with inadequate voicing become painfully obvious. Without, those inexperienced in golden age levels of differentiation tolerate flippant and ordinary voicing very easily. From your recordings, you have fine voicing skills, but I'd want to know that is the case before encouraging any other pianist to move onwards early in the learning.
The ultimate example of this is nyiregyhazi's solo sketching of the rachmaninoff second concerto. After some really rough crap the recap floats melody notes out at insanely slow speeds, as if he's got the sustain of an organist. I've never heard more beautiful piano playing than this. I think all pianists should attempt such effects, before they go on to put any sense of forward pressures on.