The goblins find themselves in a strange land after they put a mushroom in Vivalzart's machine.
Get a Drumstick
Switch to 
Winkle and click the headlight on the left side of
the room. It is just below the spring. He will get a drumstick.
Get a Pump
Then switch to 
Fingus and click on the spring. While he bounces
up and down on it, have Winkle click on the headlight again,
and he will get a pump.
Get a Net
Have Winkle use the drumstick on the stocking cap
below
and to the left of the saxophonist.
Catch a Mosquito
Then have Fingus click on the hole below
and to the left of the saxophonist. He will go to the top of the mushroom in
the upper-right of the screen. Then have Winkle use the
pump on the saxophonist, and a mosquito will come out. Have Fingus use the net on the mosquito.
Get a Musical Note
Have Winkle use the mosquito on the headlight and the
drummer will start drumming, and a musical note will appear above the mushroom
where Fingus should still be standing. Have Fingus
use the net on the musical note.
Open a Door
Have Winkle use the clothes pin on the hose in the bottom-left
of the screen. Then have both goblins stand on top of the spring, and then click
the spring. A door will open in the smiling mushroom's stalk on the left.
Get a Tune
Have Winkle go through the door in the mushroom, and he will
go on top of the mushroom on the left.
Have Fingus go into the hole on the ground below and to the
left of the saxophonist to return to
the mushroom in the upper-right
part of the room. Have Winkle talk to the guitarist, and
he will play a tune. Have Fingus use the net on the tune
(which is different from the note that you got earlier).
Get Another Note
Have Winkle click on the hole below
and to the left of the saxophonist so he goes on top of the mushroom above the
saxophonist.
Then have Fingus use the pump on the saxophonist to have him
play a tune. Have Winkle use the net on the note.
This completes the melody. You will automatically return to the clockmaker's town.
Get the Hourglass
If you don't see the melody in your inventory, switch to
Winkle and right click to put the melody back in the
inventory.
Have Fingus use the melody on the bottom-left house.
Then have him knock on the clockmaker's door (the upper-right
house), then talk to Tom. You will get the hourglass.
Use the Hourglass
Move the cursor to the bottom right corner of the screen until it turns into a door icon, and click to go to the castle, or move the mouse to the top of the screen and choose the wooden sign, then click Castle.
Have Fingus use the hourglass on the trench. Then click the
opening in the wall to the left of the castle door to have him go in. Switch to
Winkle and have him go into the opening.
You will continue on to the Castle Courtyard.