In Adobe Illustrator CS6, Gradient on Stroke was introduced. Although you can't do this in an earlier version, we're going to show you a work around for it in Illustrator CS5. We're going to do this by creating a Blend from a Gradient and even show you how to modify it using the Width Tool (SHIFT + W). We'll then go on to create a quick trumpet illustration to show you what you can do with the Gradient.
1. Create a Gradient Filled Rectangle
Using the Rectangle Tool (M), click on the Artboard to open a dialog box. Set the width to 1pt and the height to 10pt and hit OK. If necessary, delete the stroke around the new shape. Open the Gradient panel (Windows > Gradient). With the shape selected, set the angle to 90 degrees and make a gradient similar to the one shown.
2. Expand the Gradient & Delete the Clipping Path
With the shape still selected go to Object > Expand.
Now open the Layers panel and expand the Group by clicking the arrow to reveal a Clipping Path. Click to the right of the Clipping Path in the Layers panel to select it and press delete or the Trash Can icon at the bottom of the Layers Window.
3. Create an Art Brush
Next open the Brushes panel (Windows > Brushes). Select the gradient group and drag it to the Brushes panel to open the New Brush dialog box. Select Art Brush radio button and press OK. In the Art Brush Option window select a Direction arrow to the right or left and press OK. You can change these settings later if you need to by double clicking on the brush to change the settings.
4. Use the Width Tool with the Brush
With your Pen Tool (P) draw a line similar to the one shown. Open the Brushes panel(Window > Brushes) and select the brush you created to apply it to your line.
Now, using the Width Tool (SHIFT + W) manipulate the line until you get the desired effect.
5. Create Three Valves
Use the Pen Tool (P) while holding SHIFT to draw a straight vertical line for your valve. Now apply the stroke you created to the line and make the Stroke Weight equal to 0.75pt.
Choose the Section Tool (V) and while holding SHIFT + OPTION (ALT) click and drag the line a little bit to the right to create a copy. You can do this again or press CMND + D to repeat the action and create the third valve.
6. Create a Closed Path from an Ellipse
Draw a large circle with the Ellipse Tool (L). Now using the Scissor Tool (C) click the top and bottom anchor point to break up the shape.
Use the Selection Tool (V) to separate the shape while holding shift as you drag one half to the side. Try to keep the proportions the same as shown below.
With the Direct Selection Tool (A), select only the top anchor points and join the together Object > Path > Join (CMND + J). Do the same with the bottom two anchor points to close the path and create one oblong shape.
7. Apply the Gradient Brush to a Closed Path
Apply the brush to both of the new shapes only this time, for the smaller shape, make the Stroke Weight equal to 0.5pt. Position them as shown.
8. Create a Handle
Create a vertical line and apply the brush with a Stroke Weight of 0.5pt to create a handle at the front of the trumpet.
9. Create Buttons using the Width Tool
Draw a short line and use the Width Tool (SHIFT + W) to sculpt the line similar to the one shown below.
Copy the line twice so you have three in total. Then line them up with the three vertical tubes. You will need to send them to the back of the layer. To do this select all three and go to Object > Arrange > Send To Back.
Ta Da! Now You're Done!
Try different combinations of gradients, shapes and lines to create really cool seamless gradient strokes!