Equipment Choices for Orchestral Recording
Can you simply purchase a handheld portable recorder and use it, with the built in microphones? This really depends on what you find "good enough". There are significant compromises made in handheld recorders, particularly in the microphones. If you still want to go this route, there are some suggestions: Purchase a unit intended for music recording, not just for voice. The "dictation" machines record at a low sample rate and heavy digital compression that is adequate for voice, but cannot store and reproduce the full frequency range and dynamics of music. Make sure the unit you purchase can record ".WAV" files, not just MP3's at sample rates including 44.1K, and to at least 16 bit files, better 24 bit, but if you want the best quality, look for 32 bit floating point capability. If you think you might ever want to use external microphones, purchase a unit that has balanced (XLR) microphone jacks, and has the ability to provide 48 volt "phantom power" to the microphone jacks.
When you make a recording using the handheld's built-in mics, mount the recorder on a tripod or stand if possible, above the heads or in front of the audience. Although these are called "handheld recorders", your best results will come if it is solidly mounted, as any movement during the recording makes noise and degrades the consistency of the stereo image. Locate the recorder some distance back from the front of the band, try 8 to 10 feet at first. Setting it on a shelf or board is usually better than holding it in your hands, but having space around the microphones will give you better results. If you do handhold it, hold it still, don't change the "aim" from one part of the orchestra to another. Moving it around will cause the stereo "image" to shift around when you listen to the recording. That can be very distracting.
The Denon Professional handheld I own is no longer in production. Denon no longer makes handheld recorders. If you are looking for a recorder, you might want to look at some of the medium to high end recorders made by Zoom. Some are quite inexpensive for the quality. For instance, their H4 records 32 bit floating point files, has a moderately quiet mic preamp and two XLR mic jacks with phantom power. I sprung for their considerably more expensive F6, which records from six XLR mic jacks in 32 bit floating point with a very quiet mic preamp. They also make an even more expensive 8-track portable recorder with excellent specs. If you are interested in recording live surround or multi-track, either the F6 or F8n would work well if you can deal with the cost.
Assuming you do want better recordings than the built-in microphones provide, read the following pages.