How long should a concerto be?

Hi, I am in the process of composing a piano concerto and I was wondering how long it should be, I finished the first movement which is about 5 minutes minus the cadenza, but is that too short?

Absolutely not, there is no set rule for the length of concerti or seperate movements. Rodrigo wrote a guitar concerto with a movement that was no longer than 6 minutes. So just make it whatever length you see fit ;)

some vivaldi concerti are only about 8minutes in total

Will is right, but if you're wanting to accurately write within a certain idiom, then you would have to observe a certain scale or other.

For example, you might expect a first movement of a Baroque concerto to be 6-8 minutes long, whereas a classical one could be 10-15, and a romantic anything up to the mid 20s. But there's nothing strict that says "a romantic concerto 1st mvmt must last 25 minutes". It just ends up being that long because of the long discursive style that was written in.

The length of a piece is dictated by the form; so a classical sonata form concerto is usually going to depend on your starting material - you aren't going to write a development that is much much longer than your exposition, so you're always going to end with a piece in proportion to what you begin with.

Anyway, I'm kind of diverging.

Basically, if you aren't trying to write idiomatically, then you can do whatever you wish - but try to make sure the form is logical, and then the length is a secondary concern.

As Daniel very aptly noted, the length of ANY movement should be related to its successful rendering of both form and material, rather than to an arbitrary numerical value.

The final movement of Prokoviev's 4th piano concerto is, if memory serves me, around one and a half minutes long while the second movement is ten minutes. however, when you take into consideration that the finale movement is really nothing mroe than a coda to the first movement (four minutes), then its brevity makes sense... it's an echo of a previous movement (exact same themes, etc..).

A concerto, unlike a symphony, has certain formal expectations. Generally, the forms can be similar or even identical, but there is a dialogue between soloist and orchestra (even more pronounced in a piano concerto) which often means material gets MORE development in a concerto than in a symphony.

That last consideration is particularly related to how you treat your solo instrument. If the soloist is completely integrated into the orchestral texture, with many fewer solo passages, then you may get less of the dialogue effect, while if you treat your soloist as an entirely independant entity, the dialogue effect becomes more pronounced.

Also note: throughout music history, concerti for string instruments or piano have been substantially longer than concerti for wind instruments, due to the different levels of endurance that players have. Piano or string concerti have generally been as long as symphonies (in the Romantic era, usually 30-50 minutes in total length); but the length of a typical woodwind or brass concerto in the late Romantic era was on the order of 15-20 minutes.

That should be fine. For classical concerti, time varies. Mozart concerti can be from 4 min - 15 minutes per movement. As long as all the stuff is there (developement, themes, ect) and you think the movement is done musically, it's done. :)

Thanks everybody.