We need to arrange several pop rock songs. The band has vocals, acoustic guitar, electric guitar, bass, drums and keyboards. In addition, we add a trumpet. Do you have any idea, method or example of how to play the songs with the trumpet?
I suppose with a cornet you'll have the ability to add something extra in for texture, so something like finding the main melody line in the song, whether it be with guitar or vocals have the trumpet follow this line to emphasise the line and it could offer a massive difference to the sound and feel of the song depending, you should try looking at reel big fish, they get away with a trumpet
I think the answers so far spend too few consideration on the fact that we're talking here about a single trumpet added to a standard rock ensemble. Sure, there is lots of pop/rock music with brass and wind, but that is actually quite different from only having a single trumpet.
Typically, a single wind or brass instrument would only be truly capable of some solos. In some cases you might be able to mimick a full horn section and re-inforce part of a guitar riff. However, with a single trumpet, it is going to sound very thin, and you'll risk sounding like the rest of the horn backing section is on sick leave.
If the band is serious about adding wind/brass, you should consider getting either or both a (tenor) sax and trombone. This will allow you to make more background arrangements, and the arrangements can continue even when one brass has a solo. If that is not an option, I fear the trumpet will be confined to playing an intro or a solo here and there, maybe a couple of accents on a hook.
There are several examples of bands with horns (including trumpets). Going back a few decades two of the most prominent would be "Blood Sweat and Tears" and "Chicago." There's also the 70's band "Tower of Power." How about the Beatles ("All you Need Is Love")? The one-hit-wonder band "Alive and Kicking" with "Tighter, Tighter."
First question is what do you want the horns to do? Just back up the band--as in a a typical horn section?
If this is the case, the horns typically add support to the chord changes--so, you could try having the horn notes mirror the root and harmony notes of the individual chords. Many many R&B tunes are based on a I-IV-V progression--and the horns support as indicated (harmonizing against the chord changes)--and for the refrain, they typically walk down in a V-IV-Flat III-Root sequence (not necessarily single whole tones down.
If you want the horns to carry melodies, that is an entirely different question, and I think whether a horn would sound good doing that really depends on the piece--a lot of music sounds good w/ backing horns, but not necessarily w/ horns carrying the melody--just my 2 cents
Put it through some effects, like an octave lower-er or something that makes the sound very reverberaty / echoey. That way you can add ambience or texture without distracting from the rest of the composition and layers.
Check out the band Cake, they do a great job adding horn skillfully without using any sort of effects.
I have played trumpet for years, and am currently playing trumpet in a band. Trumpets have a wide range of styles they can do, so don't be afraid to experiment. Trumpets are very good for in the background or the occasional solo, but can do more than that as well, so it really depends on the song itself, and the player. If the trumpet player likes going fast and high, then its easy to give them solos and complex rhythms and that will sound fine. If they don't really like being in the spotlight, that's a bit harder because trumpet is a very attention-grabbing instrument but a quiet background is possible.