Instrumental Solos

When writing a solo for a particular instrument or section, you need to know a few certain things. 

First, any important solo that needs to stand out should always go to the first chair of the section. You shouldn’t let the 3rd horn player play a solo instead of the 1st horn player. The first players are usually the ones who specialize on the main instrument and while in a god orchestra 2nd or 3rd chair might just as well be capable of playing the solo, it is considered mandatory to give solos to the first chair. If you don't, depending on your player, you might get some upset reactions.

The only exception to that rule that might be acceptable is to save ressources in the brass section. Let’s say you want to write a trumpet solo which however gets followed by a massively demanding, high, loud, fast action passage which needs everything from the first trumpet player (for example as he/she has to play very high). In this case, you might want to give the first player a moment to rest and prepare and give the solo to the second player. 

However, I would recommend writing the solo line in cue sized notes also into the first player in case he/she might still feel up to playing it.

Cue sized note heads are generally a good idea in any cases where you are not 100% sure whether you want a solo or ensemble sound e.g. you aren’t sure whether to have a horn solo or all 4 or 6 horns playing that line. Write the solo line into the first player but put cue notes in all other horns. If you are on the scoring stage and decide you want all players but have the notes only written in the Horn 1 part, it will take quite some time or be even not possible to transfer the music in question to the other players. With the cue notes, you can save that time and just tell them “Ok, with the next run-through play the cue notes.” You should however mark these spots accordingly with word like "On Cue" at the beginning of that passage. It is adviseable to not overdo this principle. A part/score cluttered with optional cues might become very confusing very quickly and the discussion needed on the stage might eat up a considerable amount of session time. So only use this on spots where you are really unsure and want to try it out on the scoring stage.

Another important issue is to write the word “solo” on any solo line so the player knows that he/she is not playing a filling line but needs to stand out. Also, this indication will let the player know to interpret a line that might be particularly expressive with more rhythmic freedom than if he/she were playing with other players. If a section plays a solistic line, it's also a good idea to let them know by writing "Soli" at the beginning so they understand that the passage to follow is not an inner part but supposed to stand out. The indication "bring out" might achieve a similar effect and can also be used on just fragments of a line that you want to be interpreted more prominently. 

As with all indications in score sheets don't use them mindlessly. It's not neccessary to state the obvious but also desirable to guide your players through which roles in the music they take on during the piece.