How about opening 1C on that hand? That gives the most options for finding a fit: you raise 1D to 1H and 1H to 2 or 3 as appropriate.
In 2 over 1 and Standard American, a rebid of 2 of a minor promises 6, except when it doesn’t. Sometimes you might do it on 5 as being the least lie. I see from your post that you play Acol. I believe Acol is more tolerant of rebidding 5-card minors, especially if you play a weak no trump such that 1C - 1S - 1NT would be 15 - 16 points.
With 5 clubs and 4 hearts, it depends on the rest of your hand. Assuming the bidding starts 1C - 1S as the problem sequence: if 2-4-2-5, I bid 1NT (assuming I am 12 - 14. If I am 15-17, I would have opened 1NT in the first place). If 3-4-1-5, I raise partner to 2S. If 1-4-3-5, then judgment applies. With a small singleton but a very good diamond suit, I lie and bid 2D. Otherwise, I respond 1NT.
You asked about experts, not me, but I believe that the majority of experts play the same way.
Opening the suit below the singleton is how I was first taught (and I played Acol in those days). However, it does work better to open 1D and rebid 2C as long as you have an agreement that this does not show 5-4 in the minors but can be 4-4. Or you open 1H and rebid 1NT.
Your partner should not have raised you to 3C on a 3-card suit. You do not say how many points they had, but I would think pass with 6-9 and 2NT with 10-12 are better options. i.e. what OldGuy said.
That works fine as long as you are prepared to rebid 1NT if partner responds 1S.
I was also taught to open the suit below the singleton (or void). Opening the middle suit may be good enough; the important thing is not to open the suit above the shortness as my partner did with 0-4-4-5.
But aren’t five-card major openings almost universal now except in Britain? We used to check “Avoid” on the “4-card major” part of the convention card; have most of the Avoiders converted to Neverers?
For a while my regular partner and I played Canapé (Blue Team club). That adds spice to some auctions, e.g. when Opener says “Double” at his 2nd turn to show his main suit. Anyone play Canapé these days?
I think you are right, although there is some Acol played in Australia, I believe.
A couple of weeks ago I read a book by Sabine Auken written in 2006 in which she plays Canapé. However, she now plays 5-card majors with Roy Welland. When I searched for Canapé, only one pair came up - Verhees/Prooijen - so I guess Canapé has virtually died out.
The expert group with whom I play have pretty much dropped 5 card majors. I use 5 card majors there because my partner uses them and we’ve had some significant issues thereby.
I am in Britain, so that explains that. 
And I haven’t played often enough or at a high enough level for years to learn the strong NT / 5-card-major system, though I know most of the top pairs play it (I also suspect it’s better suited to matchplay - where it’s critical to find the slams - than duplicate)
Do you mean teams? In teams, it’s more critical to find the game contracts than get tops.
Yes, teams (I don’t know what I was thinking with ‘matchplay’).
At IMP scoring it’s more important to get the big hands right.
Our league starts up in a couple of weeks so I was just going over the card with my partner. It’s funny how you form you own views of what conventions / treatments are essential, yet others consider them trivial - would you say, for example, that a serious / non serious 3NT bid [or equivalent] was fundamental to a 2/1 system? I would, but my partner isn’t bothered about it at all. He recognises the concept of course, but I guess thinks 2/1 sequences are relatively rare and can normally be worked out with natural hand evaulation.
OTOH, he likes the multi and Muiderberg 2s - I suspect because they slay at the club, but they’re nothing special against good players and 3 weak 2s is simpler and better IMHO.
At the end of the day, there is probably no bridge card on earth that could not be improved by taking stuff out…
Most of my partners have 4,000+ points (US system), or are equivalent to UK Premier Life Masters or better (but I have not kept up with UK ranking changes), so are pretty good players, but I only play serious 3NT with one of them, so I would not say it is fundamental to 2/1 (in the US at least). I think it is a good thing to play, and allows you to dispense with fast-arrival in most cases, but you can live without it. And in occasional partnerships you can run into issues as to whether a particular 3NT bid is serious/non-serious or simply a suggestion to play there.
As this thread was started after making a grand slam, here’s a hats off to Andrew Robson and David Gold for one of the best bidding sequences I have ever seen. They bid and made 7D on a 4-3 fit after agreeing a 5-4 spade fit earlier in the auction. And diamonds were first bid naturally at the 7-level.
Robson Gold
AJxx KQTxx
Ax x
KQJ9 Axx
J9x AK8x
1NT - 2H (1)
3S (2) - 4C (3)
4D (4) - 4NT (5)
5H (6) - 6C (7)
7D (8) - Pass (9)
(1) transfer
(2) superaccept
(3) first or second round control, will not be shortage
(4) first or second round control
(5) RKCB. Imples heart control
(6) 2 keycards, no QS
(7) asking for third round club control.
(8) suggestion to play. Robson took 3 minutes to find this bid.
(9) pass. Gold took 5 minutes to find this.
Note that even if Gold held just Ax diamonds, 7D is still a better slam than 7S.
Robson worked out that Gold might have the hand he did, and that getting a heart ruff (and club discard on the fifth spade) would allow 7D to make. And with a different hand, Gold could convert back to 7S/NT. Gold worked out what Robson was suggesting and why, and passed.
This was also the last board in the Bermuda Bowl final. France bid 6S, making. USA2 bid 7S, down one, to lose 17 IMPs. Fortunately for the USA2 team, they were 19 IMPs ahead.
That is very cunning bidding. Just what you expect from someone of Robson’s caliber.
I wonder how the bidding would have gone if they were using a Weak NT? Perhaps 1S - 4H (splinter) - 4N - 5D (three Aces) - and I’ve forgotten about how to ask for the Queen. I suspect that that line would end up in 7S. Or would you bid 1D first? 1D - 1S - 3S - 4C - 4D - etc.
To open 1S would mean playing a system that allows 4-card major openings. Robson/Gold play 2/1, so they would not open 1S. An Acol pair opens 1S (presumably). A 4H splinter is possible but the issue is that the bid uses up such a lot of bidding space that it is best to play it with a relatively tight range, e.g. 10 - 14 HCP. Otherwise, opener does not know whether it is safe to bid on and commit to at least the 5-level. I would prefer a Jacoby 2NT bid with a stronger hand, such as the one Gold held, although some people prefer to restrict Jacoby to balance hands.
If you splinter then bid RKCB, and partner responds 5D, the queen ask is 5H (next suit up other than the trum suit). East would respond 6C, showing QS and KC as the lowest king. On this auction West does not know that East has 5 trumps, so it is hard to see them bidding 7 with any confidence. And there is no way they will get to 7D. I expect them to stop in 6S.
If East responds 2NT instead of splintering, it can go 3NT (15-17 points), 4C - 4D - 4NT - 5H - 6C. This is very similar to the actual sequence, but again the issue is that West does not know that East has 5 spades, so they are likely to stop in 6S.
Playing 2/1, if outside the 1NT opening range, West opens 1D, East bids 1S. West probably bids 3S. Now 4C - 4D - 4NT - 5H - 6C. Again, West does not know about the 5th spade, which was key to the original 7D bid - it is where West’s 3rd club gets parked. So I suspect they end up in 6S.
But who am I to state with any accuracy how players would bid in the world championships? I have not played in any such championships myself.
5 card majors are a pain in the butt, but we’ve been over that before. 
Played in a decent teams congress at the weekend and picked up the following:
S ATxxx
H x
D AKx
C KJxx
All non vuln, IMPs, good opps. Partner obliges by opening 2NT, 20-21.
What is your approach? Could this be the one auction per year where you dust off gerber?
2NT is 20-22. You have 15 HCP so bid 5NT which is a demand to partner to bid 7NT if maximum or 6NT if not.
Otherwise you could bid 3H as a transfer to Spades and after parner’s response bid 4NT to ask for aces, ending in 6NT or 7. If partner shows enthusiasm for spades by responding 4S you might prefer 7S as a contract.
2N is 20-21 here, as stated. So 5N transfer of responsibility will be hard for them to evaluate.
Jacoby transfer would see pard bidding 3S, suggesting he does not love the spade suit. An immediate 4N would then be for spades, but you could prob convert to 6N if you liked.
I’m interested in the team psychology of it more than anything - checking for aces, hearing 4 and then ploughing 7 must have chances, and in a pairs game I’d be happy doing that. Teams, though - it’s very expensive when it’s wrong and will bomb morale if you can’t justify it with an intelligent auction.