Music selection for an exam/audition is one of the most important you can do. Choose easy pieces and you might be accused of “playing it safe” Choose harder ones and you might be criticised for overextending yourself or being overambitious. Then there’s choosing pieces that you can play but are well known. You might be caught out and seen as not understanding the music if it’s a famous work or even be thought of as unimaginative if it’s something many others have played before (e.g. think choosing ‘Fur Elise’ for an exam/audion. If you don’t know the tune, Google it. You almost certainly would have heard it before).
When preparing for an exam/audition, consider the number of pieces required. Most music exams require at around 3 pieces (in the UK under the ABRSM exam board at least. With other countries this may vary). If you are required to perform multiple works, you must start thinking about how all will showcase your best playing qualities.
The piece needs to reflect your best musical qualities. This could be how expressively you play, paying attention to the dynamics or just showcasing your flair for technical wizardry. You must play to your strengths. No point choosing a piece you don’t like and will not enjoy playing.
Your chosen works also needs to have contrast, especially for exams. If choosing an up tempo work, choose the opposite for the other piece. If your performance requires three pieces, choose something that ends as you started, e.g. if you began with a slower work, have a fast piece in the middle then end with another slower piece, ideally with a bit of difference . Alternatively, you can choose an up, mid and down tempo collection and start with the slow work, ending with the fastest piece.
Although it usually isn’t an issue with exams as most pieces are similar length, with auditions and competitions, it can be down to the musician to decide what they play so you need to consider how it will come across to the examiner/judges/adjudicators (as well as any audience present). The works naturally shouldn’t drag on to the point where you lose everyone’s interest. Also, if you’re required to play from memory, then the longer the chosen pieces are, the more risk there is for mistakes and memory lapses so think how long you can play from memory for. A short work of 1-2 pages executed well will probably work better than a 4 page piece where the last page and a half show mistakes or expose any weaknesses in technique or memory.
If you intend to play a famous piece, think how you can put your own personality into the performance. Unusual as it sounds, rather than play to impress others, think about yourself and how you would enjoy the piece while playing. It doesn’t require a huge deviation from how the piece is written but little details like how you play notes, rhythm and speed (if there are any indications in the piece) and of course dynamics are areas you can play about a bit with to make the music seem ‘fresh’ even if it’s been heard many times before. To get you started, I suggest looking up online videos of performances of the pieces you intend to play, specifically multiple versions from different performers. If you’re serious, you will do this because you’ll soon see how a piece of music can be played many ways by different musicians.
Ultimately, your selection will be dependent on how much is in your repertoire, what you enjoy and what you are most comfortable with (to the point where you could play the pieces from memory if necessary). Above all, focus on enjoying what you play and don’t get too bogged down in what will impress others as how you perform (esp with enthusiasm and confidence) will matter more in the bigger picture.