Playback Help

Take a look here: https://musescore.org/en/handbook/hairpin in particular to the last paragraph.

In any articulation, if you click on them, you will see a setting for "Time stretch". This is a multiplicative factor as to the duration of the note- at the default of 1, the note plays at the same speed as before. At 2, it plays twice as long (the metronome speed is cut in half), at 0.5 it plays half as long (metronome speed is doubled) and so on. Fermutas are actually nice in that they lack any other playback; you can place invisible ones all throughout a score to modify, on a note-by-note basis, the exact speed you wish the note to be played. As for crescendos and decrescendos, you must have a dynamic following each. Whether you use the text line or the hairpin, some form of dynamic must come between the end of one cresc/decresc and the next. If necessary, you can adjust the cresc/decresc so that it ends a note earlier than the notation would indicate, and you can cram in an invisible dynamic. This is useful for measures with a "swell" in the middle of the piece. Lines such as cresc/decresc and pedal lines can be modified by double-clicking them after placing, clicking the end of the line (or the beginning), and holding shift + using the left and right arrow keys. This will adjust the "anchor" of the effect, i.e. where the effect starts and stops in terms of notes. Dragging these will not change the anchor position, so be sure to use the arrow keys and shift. Otherwise, you'll end up with dynamic changes that don't actually work.