It seems to me that people who learn certain instruments first will progress much faster in another instrument if the 1st instrument has "complementary value" to the 2nd, while there are some instruments, if you learn them at the same time, one might get into the way of another, or, the more you progress in one, the more you loose out on the other.

My friend who is a pianist just passed grade 8 flute within one year of learning the flute. She has no prior experience with woodwind instruments. I can only conclude that her piano background must have helped her progress trememdously.

These are some of the instruments which i think are complementary to each other, and their complementary ratings. My ratings range from -3 to 3. Where 3 is the most complementary, -3 is the most uncomplementary, meaning that learning one instrument will get into the way of the other very much. For example, it is difficult to be both good at the flute and trumpet, as they require very different embouchure.

1st instrument / 2nd instrument (Complementary rating)
piano / any other instrument (2)
Piano / singing (3)
Violin / Viola (3)
Violin / Cello (-1)
Flute / trumpet (-3)
Guitar / violin (-1)
Guitar / Cello (1)

interesting...........
i learn violin before piano....it helps a little at the beginning stage.

I'd put the combination I play as a -1
Piano / piano accordion
Yes they are both key boards but one is a horizontal keyboard the other vertical and the piano accordion keys are slightly narrower so all the stretches are different

Why is guitar/cello a better pair than violin/cello? I would have thought it to be the other way around?

Just felt that the guitar and the cello have rather similar thickness in their strings, so the left finger touch of playing the cello and the classical guitar is not that much different.

Although the violin and the cello are both bowing instruments with four strings. Bow pressure and bow grip on the violin and cello is very different. Finger touch and sensitivity is also very different between the two instruments, since the thickness of the strings between of instruments are so different. Seldom heard of anyone being proficient in both violin and cello at the same time of their lives.

clarinet and saxophone are very complentary

I was waiting for that reply from you!!!

Flute and piano are complementary.... I think

I agree with clarinet and sax, though I would say clarinet and bassoon are -1. Piano is complimentary to most.

Guitar and cello are not complimentary. I know someone from my undergrad degree who was not allowed to learn cello and guitar when she was learning.

I think generally learning instruments from 2 different sections of the orchestra (counting piano as a seperate section) is complementary. Learning two similar string instruments can become confusing, say cello and double bass. Learning double bass had a negative affect on my cello playing, definitely. At the mo, I play violin and drums primarily, and they are ever so useful together. I learn to play in an ensemble and to read strange time signatures and rhythms well from kit, and learn the more musical elements on violin. Then I can apply one to another. My sight-reading benefits very much from the combination.

Being a guitarist..... I don't think cello would really be under compatible instruments (even if the cello wasn't compatible with violin).

I would say that guitar strings are probably closer in thickness to viola strings than cello strings, actually.

Maybe cello would be slightly compatible with bass guitar though, it has much thicker strings and reads the same clef.

Of note, Paganini was also a brilliant guitarist

Clarinet and bassoon are definately not on the compatible end of the spectrum! Of all the embouchures to stick together, it's not exactly ideal!

True though!

Clarinet and sax - definitely. Flute and recorder - probably. What about clarinet and flute, though?

So was he a brilliant violinist!
So violin and guitar are not that uncomplementary after all, at least for him.

I heard from dunno where that Paganini considers the violin his master, while the guitar, his mistress.

I know some people find mixing clarinet and flute a problem - tends to create more probs on the flute side of things than the clarinet side of things, with embouchure.

Clarinet and flute: 0 (They have barely anything in common, but neither hindered the other for me)

Recorder and flute: 2

Recorder and sax: 2

Sax and flute: 3

Clarinet and sax: 2

Recorder and clarinet: 1

Piano and all of the above: 1-2

I also play the violin and viola, and sing, but all are relatively recent and just for fun (got grade 4 on those three) and mess around on the guitar, which I'm rubbish at and doesn't help with my violin playing!

How can you say

clarinet and flute - 0

sax and flute - 3

the only thing i can see that sax and flute have in common is the fingering

is has a different embouchure just like clarinet

Maybe that's just the way it worked for me. After studying the flute for a couple of years I started the saxophone in March (I think this was in 2002) and passed grade 5 in June with 139 marks, because of my flute playing. Maybe the interaction between clarinet and sax blowing helped too (I'm sure it did). But out of all the wind instruments I play, the fingering between flute and sax are the most similar. It makes the scales almost identical until you get up to the very top.

I have a friend who plays the Violin, Cello, Clarinet, Piano, Alto Saxophone, Soprano Saxophone, Percussion, Guitar and a few notes on the trumpet. She has no trouble playing any of the instruments and is even wanting to play another instrument (possibly a brass instrument).

The composer Paul Hindemith allegedly was able to play virtually all the instruments of the orchestra to a reasonable standard. I don't think this gave him any particular insights or expertise in orchestration, unfortunately, and his orchestral works don't have any particular brilliance or subtlety in their orchestration. His own instrument was the viola, and he premiered Walton's superb Viola Concerto.