With the GT40 at Le Mans - difficult to beat this

The Ford GT40 is one of the all time best sportscars ever. Not only did it win Le Mans more than once it also successfully competed on many other racetracks around the world. And you could even drive the car on the road. It looked good as well, but, Gee, the sound was just incredible, as the enclosed (not new) video from a lap at Le Mans (Classic 2008) clearly points out:

The black art of engine sound engineering

When today's car engineers design a car, sound engineering is an important competence to include, especially when we look at sport cars. The engine note and exhaust system of an Aston Martin Vantage V8 or DB9, Ferrari California, Maserati Gran Turismo and of many others are optimized to generate a characteristics and sporty sound pattern. Some of these engineers succeed, others don't. It seems that eight and twelve cylinder engine offer the best base, but Lamborghini has proven that V10s can sound interesting as well. And what about six cylinders? Well, they usually are part of less expensive car packages and less effort is spend to make them sound great. Exceptions are BMW (with their marvelous straigh six engine, for example in the new Z4) or Volkswagen with the R engine.
In the past it was much easier. Add hot camshafts, bigger carburetors and get rid of most of the exhaust system (something that is simulated again today by adding pneumatic controls). Listen to the Porsche Carrera 6 here, unforgettable!

Why do cars sound good or dull?

Great engine sound is one of the key ingredients that make an impressive car. And many even see it as music, as the artist's picture shows here. The difference between what you can hear from a Porsche Carrera RS 2.7 (1973) and a Porsche 996 (2003) is mind boggling.
Here are a couple of hypotheses to be debated:
(1) The more fuel efficient an engine the more boring the sound
(2) Straight six cylinders sound better than V6
(3) Sound engineering helps
(4) Modern electronics will replace the "natural" sound to compensate for what's missing

To make an example for (1): When you replace carburetors by a fuel injection the sound becomes less attractive, as you can see with the Ferrari 308 GTSi versus the 308 GTS, or the 512 BBi versus the 512 BB. When you improve the engine efficiency by adding a direct fuel injection then it gets worse even. So, what has been won in efficiency is lost on sound all to often. Partially this was compensated by adding technology to the exhaust system, which proves (3). Look at all the Aston-Martins and most modern Ferraris. Ever listened to a Jaguar D-Type or a JWF Milano GT? Both have straight six engines and sound great. Same with BMW engines, neither Mercedes nor Audi have been able to compete with BMW in terms of sound quality. Modern technologies such as loudspeakers in exhaust systems (and the car interior) plus sound generation computers will more and more add what is missing from the mechanical department. Which is what I mean with point (4).
But, whatever the modern sound engineer will be able to do, it doesn't replace the sensation we have listening a vintage car or 60ies sportscars driving by. Noise/music coming from mechanical components and open exhaust systems will always sound better.

The Alfa Romeo GTV 6 - best post-80ies Alfa soundtrack

The Alfa Romeo GTV had been around for quite some time when they decided to put the 6 cylinder from the Alfa Sei into it. And this totally changed the car and its positioning.
The Alfa Romeo GTV 6 was directly competing with the contemporary smaller Porsches and for example the Renault-Alpine A310. The price point was set at around half the value of a Ferrari 308 GTB, so it was somewhat affordable.
The Alfa Romeo GTV 6 is a car where the engine is (almost) everything. And what an engine this was! In the GTV 6 disguise it developed roughly 160 HP, featured a fuel injection and produced an unbelievable soundtrack. Different to other cars where you need to wind down the windows this soundtrack is always extremely present also in the interior and reason enough, not to order a stereo for this car. Why should you? The rest of the car was okay but not really great. The transmission mounted in transaxle setting was difficult and not exact to operate. Breaks and suspensions were acceptable but not really performance car like. The interior was improved against the older GTVs but still much less attractive than for example what came from the UK at this time or even partially from Germany.

But as a package it was a great car and the reviews from the different car magazines were quite positive, again especially for the engine. Fuel consumption was quite low too, performance with roughly 8 seconds from 0-100 km/h and 220 km/h top speed pretty competitive during the early 80ies. There was a kind of Mark 1 and a Mark 2 (with more plastic and some improvements). It was built between 1981 and 1986. Rust and corrosion were still a topic but less so than for the years before. The car sold quite well.
I haven't yet owned a GTV6, but it's one of the 80ies Alfas to consider and I believe there hasn't been one since then (maybe with the exception of the outrageously expensive 8C) that sounded as well as the GTV6.