In Practica Musica exercises, choosing from the clef, key, or meter box choices will automatically change the corresponding item in the exercise staff. But if you're using a writing activity to compose your own music you have more flexibility: you can place a change of clef, key, or meter anywhere in the music, and you can change an existing sign by selecting it and choosing the new one.
The Clef tool
When you click on the Clef button a window will appear with every clef that you could ever want, as well as some you will probably never use. Slide the mouse to highlight the desired clef and let go to select it:
If you change clefs, all the notes following the new clef will instantly transpose to the correct positions for that clef.
To quickly change an existing clef just select it and then choose a new clef. The new one will replace the old.
Clef changes can be entered as frequently as you desire when using one of Practica Musica's writing activities. If you're at a line break it's best to put the clef change at the end of the previous measure, so that the reader is warned of the upcoming change.
When you choose a key signature from the popup window be sure to choose between the major and minor keys that share the same key signature: this could be part of your answer if you're doing an exercise.
As with clefs, when in a writing activity you can enter a different key signature as many times as you like within a composition. If you put a change of key in a score it is customary to enter a thin double bar to mark the division.
To quickly change an existing key signature just select it and then choose a new key. The new one will replace the old.
Select a meter signature from the popup menu and enter it in the same way as described for clefs and key signatures. Changes in meter should take place at the end of a full bar of the previous meter, though when using the notation tools Practica Musica will allow you to put the change wherever you like. If you don't see the meter you want in the meter popup, you can make your own using the "other" meter choice.