The area of the snowsong spell (Frostburn, p. 105) is listed as "30-ft. radius centered on you". Does this mean that the spell moves with me once cast?
This seems like an amazing spell, but only if it moves with me. I have yet to find anything online to tell me whether it does so or not.
Were the snowsong spell effect to move with the caster, the spell would likely have header entries like those of the 6th-level Sor/Wiz spell antimagic field [conj] (PH 200) and be, instead, an emanation: "An emanation spell functions like a burst spell, except that the effect continues to radiate from the point of origin for the duration of the spell" (PH 175). The snowsong spell effect's not an emanation and has no special rules saying otherwise, so its effect stays where it was put like most other non-emanation effects that don't specify otherwise.
In other words, the 6th-level bard spell snowsong [evoc] (Frostburn 105) creates an immobile area. Although the spell's area is measured from the caster, like the similar 1st-level Sor/Wiz obscuring mist [conj] (Player's Handbook 258) and the extremely similar 6th-level bard spell dirge [evoc] (Spell Compendium 65), the snowsong spell effect is stationary.
Just to be clear, the snowsong spell's description begins with the following:
When you cast the spell, you must designate all creatures in the area as either allies or enemies. (Fr 105)
And it ends with this:
These benefits remain in place as long as the spell persists and as long as the target remains in the spell’s area. If a creature leaves the spell’s area, all effects end for that creature until it returns to the snowsong’s area. (ibid.)
(Emphases mine.) Needless to say, casters usually designate themselves as allies and tend to want to stay in that area. (Its immobility is also likely why this guide lists the snowsong spell as only an average spell choice for the typical bard.)
Note: While the mist spell's description says that its effect "is stationary once created," this reader assumes that this reminder is because of the spell's status as a 1st-level spell, its clarification right there so players new to the spell needn't look up these rules. Because of its Range entry a DM may rule that a caster can affect spells like obscuring mist and snowsong with the Complete Arcane feat Persistent Spell (81) (see, for example, here; in such cases, effects would remain for 24 hours right there where they were cast, totally immobile.
While snowsong is not explicitly defined as an emanation anywhere in its text, it was probably intended to be one (and thus move with the caster), because that specific wording you quoted is most likely a misprint.
Firstly, any spell with fixed area and range entries that is explicitly centered on the caster is consistently described as a burst, spread or emanation throughout 3.5 sources. That "radius centered on you" wording with no other clarification would make snowsong the only exception in published 3.5 material. This strongly points to sloppy editing as the most likely cause for the omission.
No term or sentence in the spell's description unambiguously indicates whether the effect is static. In fact, the way snowsong works seems to suggest otherwise: like any emanation, it affects only creatures entering or remaining in the area, as the spell's text clearly states.
Considering area+range, effect and duration, the spell most closely resembles other buff auras centered on the caster, which tend to move with the character unless otherwise specified. Examples include aura of evasion and cloak of bravery from the Spell Compendium or linked perception and longstrider, mass from the Player's Handbook II, among others. Even the dirge spell, used in the previous answer as an example of a spell similar to snowsong, is quite oddly a burst that actually behaves like an emanation. This is likely due to a slip by the designer updating the original Magic of Faerun version, which shows how unfixed errors are common in spell descriptions.
While none of this rules out other interpretations completely, snowsong being an emanation that moves with the caster as point of origin would be both the simplest explanation and the most consistent ruling considering how similarly worded spells usually work. That said, given the spell's ambiguous text and the lack of any official errata or FAQ, any DM will probably still want to have the last word about it.
