Feel like I may mislead you a bit my music theory is pretty rusty.

I believe if I remember right it has to do with being in certain clefs and keys. I think the biggest thing was playing in concert pitch specially when tuning so everyone was in tune. Transposing it is refereed to as well sometimes.

I was going to mention that if I re call right piano and guitar are considered “C” instruments so when if we both play same note or chord like a G note or such we don’t need to transpose. They will sound the same.

Again I haven’t looked at this stuff in forever or practiced it so I’d suggest you read more into it. Or least someone can give a better answer. Hope it gives you a good start.

The G note on a piano is well tempered. The standard pitch of an A note is 440 Hz. You start multiplying 440 with the twelfth root of two (about 1.05946309435929). Wind instruments work with overtones, e.g. 220, 440, 660 etc. So you always get normal fractions when looking at musical intervals (rational numbers), which are slightly different than well-tempered pianos (irrational numbers).

“Here” is a wiki article about transposing instruments, which @CuriousLoner was discussing above.

Saxophone is a transposing instrument. What this means is that the music written on a saxophone staff creates a different pitch than it would on a piano. From what you have said, I can tell that it is either a tenor saxophone or a soprano saxophone written in the key of Bb. This means that a C on the saxophone is a Bb on piano, and all of the notes are likewise shifted two half steps.

Why would different instruments create different pitches for the same note? There are several reasons, but I believe that the wiki article does a good job explaining it.

Also, it is important to note that @mattbrowne‘s answer does not explain the phenomenon in the question. Rather, it explains the existence of musical commas, which are small deviations caused by tuning differences. These two things are of different orders of magnitude. A comma is a few hundredths of one semitone, while the transposition described is on the order of two semitones.

@AshlynM, Because of the size and sounds, many instruments are “pitched” with their “C” at a different note relative to the piano, or concert pitch, and therefore are called transposing instruments, as @PhiNotPi said. From what you’ve said, I’m guessing your friend has an E♭ Alto Saxophone, which means the C on that sax is an E♭ on the piano. String instruments are pitched in “C”, although they may use a different staff or clef. Trumpets and tenor saxophones are pitched in B♭, alto and baritone saxes are in E♭. A soprano sax is usually pitched in C. Lower brass, such as trombones, baritone horns and tubas, while pitched in B♭, are usually notated in concert pitch.

Oh, yes, he would not be in the key of Bb, since the notes were G and Bb. For some reason, I thought he said C and Bb.

Both notes should be at the same pitch but would sound different because the piano is a string instrument and a saxophone is a woodwind instrument. If they do sound different pitch-wise, one or the other is out of tune. Since your piano is digital, it doesn’t go “out-of-tune” so the sax is the one that is “out.” If I remember correctly, to tune the sax, you reposition the reed.