Whatever sounds the best for the melody or part that it needs to play in a particular song or composition. Basically, whatever gets the job done.
BASS: Sometimes a fretless bass is better suited, other times an acoustic bass does the trick. But most of the time, the good old metal bass is required to give the song the required power and depth. And yes, any and all kinds of bass can – and most of the time will – be played with a pick against you.😉
GUITAR: There is no such thing as classical vs electric guitar – each can have its place and its own parts to play – as evidenced in the song “In the Night Sky”. Howver, there is no such thing as acoustic guitar in any Wrong Destiny songs – and don’t expect to hear an acoustic guitar here any time soon. The harsh steel strings on an acoustic guitar are the main reason why too many people give up on playing the guitar. The same goes for roundwound strings on the bass.
OCARINAS: There is always more than one ocarina on a song. Due to the physics behind their resonating chambers, ocarinas have a limited range, and it is better to use single-chambered (12-hole) ocarinas for different melody registers than to use a triple or quadruple chamber ocarina to try to cover the entire song – at least for recording purposes.
KEYBOARDS: Unless you are a classically trained pianist, just get yourself a decent, light weight 88-key MIDI controller, and operate whatever samples make you happy.
However, an inexpensive classical guitar, bass, or ocarina can sound better than similar instruments two or three times the price – it all really depends on how you record them and how you process them in the mix.