How did the alto saxophone change since it was invented?

Answer 1

Of course. Some big changes, some little.

The first saxes (1840's) only went down to a low B, so the bell was a bit shorter and had no Bb key.

Early saxes weren't lacquered, they were bare brass. Silver plating came next then lacquer.

Until about 1911, there were two octave keys, one for notes up to G and one for higher notes. Now there's an articulated mechanism that opens different octave tone holes with a single key.

Rollers on the pinkie keys were added in the early 1900's

Until the 1930's most saxes had one bell key on each side of the bell.

The articulation of the G# and C# pinkie keys was added later

The front high F# key is a recent additon.

Key guards used to be made of brass rod. Now they're sheet metal.

Many changes in bore dimensions, tone hole placement and key work, most barely noticeable.