To add to Vi's list of no-nos on an arranger:
1- When playing a wind instrument, a common error is to play a phrase for a lot more than 15 seconds or so. Remember, all wind instrument players (trumpet, trombone, flute, clarinet, oboe...) need to breath. They can't just play a one minute phrase without several quick pauses. A common error is to play one l-o-n-g legato phrase with these voices.
2- Vibes or xylophone - play with two fingers. These players don't play full chords, although, Peter Appleyard perfected the holding of multiple mallets in each hand, so there are some exceptions. Also, I'm not sure those guys play grace notes either. Perhaps someone can correct me on that.
3- String pads are a contradiction in terms. I never use them. It's impossible for strings to sustain notes through an entire song. Violin bows change direction and you can hear it. String pads, if real, would need a bow 1,000 feet long for a 3 minute song! Turn them off. They completely destroy the sound.
@Lee:
Actually a very good vibraphonist can play up to four notes at once with two mallets in each hand but you have to be a true virtuoso to do this! Listen for instance to the great jazz vibraphonist Gary Burton. But I dont have a clue as about which notes can be played together. Obviously, both notes played by the same hand may not be too far appart.
As for wind instruments, there is another problem, the sound attack and evolution of the sound over time. A French guy called Jean-Claude Risset, who was both a composer and a sound engineer, devoted years of his adult life to the modelisation of wind instruments with computers (he worked some time in the Bell Labs with the American engineer Max Matthews to achieve this). It is one of the most difficult things to achieve. Now, on recent Yamaha keyboards, off course you have the SA1 and SA2 voices, but to correctly use them, you need at least some basic knowledge of how wind instruments are actually being played, otherwise the result will sound clumsy.
(By the way and off topic, Risset was a lover of Yamaha instruments, he composed some intricate piano pieces for the DiskClavier pianos were the music being played by the pianist interacts with the DiskClavier through a software which Risset and his staff programmed to this effect.)
As for string pads, it depends. Of course, if you want to mimick a real string section you won’t use them, but since the mid-seventies, we have been used to pop music heavily relying on string pads provided by analogue, then by FM synthesizers, then by other synthesis techniques, including sampling of real string instruments, so I guess it is alright to use them depending on the type of music you are playing.
@Mark:
Of course, if you do not care about how real instruments actually sound, you can do what you want, but it is still best to have an accurate hear and at least some command of harmony if you want the overall effect to be pleasant. For instance, a combination of piano and strings has been usual in New Age and church music for some time now and it can sound very nice. But to play electronic music as such, IMHO an arranger should not be the instrument of choice, because its sound palette might be too limited, it would be best to work with a synth or a worstation, or on a powerful computer with VSTs.
Best regards,
Vinciane.