Vocal Range
The main difference between mezzo-sopranos and first sopranos is their vocal range. Mezzo-sopranos typically have a lower range than first sopranos, and they may also have a wider range overall. The average vocal range for a mezzo-soprano is from A3 to A5, while the average vocal range for a first soprano is from C4 to C6.
Voice Quality
Mezzo-sopranos typically have a richer, darker tone than first sopranos. They may also have a more powerful voice, although this is not always the case. First sopranos typically have a lighter, brighter tone, and they may also have a more agile voice.
Musical Roles
Mezzo-sopranos and first sopranos are often cast in different roles in operas and other musical productions. Mezzo-sopranos are often cast in roles that require a strong, powerful voice, such as Carmen or the Witch in Hansel and Gretel. First sopranos are often cast in roles that require a light, agile voice, such as the Queen of the Night in The Magic Flute or Gilda in Rigoletto.
Of course, there are always exceptions to the rule. Some mezzo-sopranos may have a very high range, and some first sopranos may have a very low range. Ultimately, the best way to determine whether a singer is a mezzo-soprano or a first soprano is to listen to their voice.