Become a composer! Part 2: Learn Your Instruments

[MetalRenard]

There's no bass solo in this, that was a combination of rhythm guitar and bass working together with the lead playing a complimentary rhythm. It's actually a pretty complex piece of music but it was the clearest to understand in this sense.

Now to apply it to an orchestra.
The strings in this case would be the ones creating the context, to put it in other words. They create a frame for you to insert a lead melody which is played by another instrument. This could be another set of strings (violin solo for example), a flute, trumpet, piano... Whatever.
The whole point is that it's important to understand what each instrument can do and how you want to use it in your song. :)