Left hand semiquavers

[porcupine]

I'm currently learning Mozart's A minor piano sonata K310 and I'm getting stuck with four bars of left hand semiquavers (bars 45 - 48), I just can't seem to get them nice and smooth at the right speed. Slow practice - no problem. Up to speed - rubbish!
Can anyone suggest some good exercises to achieve this? At speed, my left hand just seems to go really tense and siezes up.

[larapool]

On a similar note, I have trouble with the left hand semiquavers in Mozart's K545 first movement, the very fast left hand semiquavers that are supposed to be quiet, I just can't seem to keep the volume at a consistent low at that speed 

[lostinidlewonder]

Try playing the Lh with a skipping rhythm and then reverse it.

instead of:  da da da da
play:          daaaaaa da daaaaaa da
reverse:      da daaaaa da daaaaa


where da's are the individual semiquaver notes in the LH However long or short you play the notes is up to you but you must keep your playing totally controlled and consistent.

 I find this type of exercise with rhythm can actually exercise your hand and trick the brain into playing it more smoothly, it may also highlight to you more clearly your trouble notes. You can experiment with different held notes and even remove them and play more of the passage without the rhythmic alteration.

This sort of tactic I use for long strings of single note runs often with my own work and with my students to help gain control.