Yes. ;-)
What's important is that you know how big the sound source *should* appear to your ears.
A solo violin or clarinet is good, unless it's multi-miked or miked so close (think Heifetz) that it's unavoidably larger than life. A solo mezzo or soprano recorded in a live space (not a booth) also works well. Higher pitched piano notes work too, if the system has enough resolution to portray all the different sounds that make up a piano note.
The most challenging things I own with these types of sounds are Harmonia Mundi LPs of solo counter-tenor accompanied by alto recorder, recorded on two mikes in a vast, echo-ey stone space. A proliferation of similarly pitched tones, differing only slightly in timbre, is followed and surrounded by multiple echoes. All these similar waveforms want to interfere with each other, which makes a torture test few systems can handle. Most collapse into fingernails-on-slate screechiness. If a system is up to playing these LPs clearly (I've only heard 2 or 3 that can), they're a superbly revealing test of azimuth (and most other parameters).
