<?xml version="1.0" encoding="utf-8"?>
<!--Generated by DFIN XBRL Instance Document - http://www.dfinsolutions.com/ - Version R3.0 - on 03-March-2026 [03:23:15] {AM}-->
<schema targetNamespace="http://www.test.com/20251231" elementFormDefault="qualified" xmlns:cik0001190935="http://www.test.com/20251231" xmlns="http://www.w3.org/2001/XMLSchema" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xl="http://www.xbrl.org/2003/XLink" xmlns:us-gaap="http://fasb.org/us-gaap/2025" xmlns:country="http://xbrl.sec.gov/country/2025" xmlns:currency="http://xbrl.sec.gov/currency/2025" xmlns:dei="http://xbrl.sec.gov/dei/2025" xmlns:exch="http://xbrl.sec.gov/exch/2025" xmlns:naics="http://xbrl.sec.gov/naics/2025" xmlns:sic="http://xbrl.sec.gov/sic/2025" xmlns:us-types="http://fasb.org/us-types/2025" xmlns:stpr="http://xbrl.sec.gov/stpr/2025" xmlns:deprecated="http://www.xbrl.org/2009/arcrole/fact-explanatoryFact" xmlns:srt="http://fasb.org/srt/2025" xmlns:srt-types="http://fasb.org/srt-types/2025" xmlns:dtr-types="http://www.xbrl.org/dtr/type/2024-01-31" xmlns:cef="http://xbrl.sec.gov/cef/2025" xmlns:cef-pre="http://xbrl.sec.gov/cef-pre/2025">
  <annotation>
    <appinfo>
      <link:roleType roleURI="http://www.test.com/role/N2SeniorSecurities" id="N2SeniorSecurities">
        <link:definition>1001 - Disclosure - N-2 - [Senior Securities]</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.test.com/role/N2InvestmentObjectives" id="N2InvestmentObjectives">
        <link:definition>1002 - Disclosure - N-2 - [Investment Objectives]</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.test.com/role/N2SharePriceTable" id="N2SharePriceTable">
        <link:definition>1003 - Disclosure - N-2 - [Share Price Table]</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.test.com/role/N2OutstandingSecurities" id="N2OutstandingSecurities">
        <link:definition>1004 - Disclosure - N-2 - [Outstanding Securities]</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:linkbase id="lnk" >
        <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/cef/2025/cef-2025.xsd#N2" roleURI="http://xbrl.sec.gov/cef/role/N2"  />
        <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/cef/2025/cef-2025.xsd#SecurityOnly" roleURI="http://xbrl.sec.gov/cef/role/SecurityOnly"  />
        <link:roleRef xlink:type="simple" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedLabel" roleURI="http://www.xbrl.org/2009/role/negatedLabel"  />
        <link:roleRef xlink:type="simple" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedPeriodEndLabel" roleURI="http://www.xbrl.org/2009/role/negatedPeriodEndLabel"  />
        <link:roleRef xlink:type="simple" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedPeriodStartLabel" roleURI="http://www.xbrl.org/2009/role/negatedPeriodStartLabel"  />
        <link:roleRef xlink:type="simple" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedTotalLabel" roleURI="http://www.xbrl.org/2009/role/negatedTotalLabel"  />
        <link:roleRef xlink:type="simple" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedNetLabel" roleURI="http://www.xbrl.org/2009/role/negatedNetLabel"  />
        <link:roleRef xlink:type="simple" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedTerseLabel" roleURI="http://www.xbrl.org/2009/role/negatedTerseLabel"  />
        <link:roleRef xlink:type="simple" xlink:href="http://www.xbrl.org/lrr/role/net-2009-12-16.xsd#netLabel" roleURI="http://www.xbrl.org/2009/role/netLabel"  />
        <link:presentationLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/cef/role/N2" >
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/cef/2025/cef-2025.xsd#cef_AllRisksMember" xlink:label="loc_cef_AllRisksMember_200074" />
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_200072" />
          <link:loc xlink:type="locator" xlink:href="cik0001190935-20251231.xsd#cik0001190935_ArpsMember" xlink:label="loc_cik0001190935_ArpsMember_200582" />
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ClassOfStockDomain_200072" xlink:to="loc_cik0001190935_ArpsMember_200582" use="optional" order="1" preferredLabel="http://www.xbrl.org/2003/role/label" />
          <link:loc xlink:type="locator" xlink:href="cik0001190935-20251231.xsd#cik0001190935_CommonSharesMember" xlink:label="loc_cik0001190935_CommonSharesMember_200581" />
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ClassOfStockDomain_200072" xlink:to="loc_cik0001190935_CommonSharesMember_200581" use="optional" order="2" preferredLabel="http://www.xbrl.org/2003/role/label" />
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_AddressTypeDomain" xlink:label="loc_dei_AddressTypeDomain_200069" />
        </link:presentationLink>
        <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"  />
        <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/cef/role/SecurityOnly" >
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_200072" />
          <link:loc xlink:type="locator" xlink:href="cik0001190935-20251231.xsd#cik0001190935_ArpsMember" xlink:label="loc_cik0001190935_ArpsMember_200582" />
          <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_200072" xlink:to="loc_cik0001190935_ArpsMember_200582" use="optional" order="1" />
          <link:loc xlink:type="locator" xlink:href="cik0001190935-20251231.xsd#cik0001190935_CommonSharesMember" xlink:label="loc_cik0001190935_CommonSharesMember_200581" />
          <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_200072" xlink:to="loc_cik0001190935_CommonSharesMember_200581" use="optional" order="2" />
        </link:definitionLink>
        <link:labelLink xlink:type="extended" xlink:role="http://www.xbrl.org/2003/role/link" >
          <link:loc xlink:type="locator" xlink:href="cik0001190935-20251231.xsd#cik0001190935_ArpsMember" xlink:label="loc_cik0001190935_ArpsMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_cik0001190935_ArpsMember" xml:lang="en-US">Arps [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_cik0001190935_ArpsMember" xlink:to="lab_cik0001190935_ArpsMember" />
          <link:loc xlink:type="locator" xlink:href="cik0001190935-20251231.xsd#cik0001190935_CommonSharesMember" xlink:label="loc_cik0001190935_CommonSharesMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_cik0001190935_CommonSharesMember" xml:lang="en-US">Common Shares [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_cik0001190935_CommonSharesMember" xlink:to="lab_cik0001190935_CommonSharesMember" />
        </link:labelLink>
      </link:linkbase>
    </appinfo>
  </annotation>
  <import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd" />
  <import namespace="http://www.xbrl.org/2003/linkbase" schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" />
  <import namespace="http://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd" />
  <import namespace="http://xbrl.sec.gov/dei/2025" schemaLocation="https://xbrl.sec.gov/dei/2025/dei-2025.xsd" />
  <import namespace="http://www.xbrl.org/dtr/type/2024-01-31" schemaLocation="https://www.xbrl.org/dtr/type/2024-01-31/types.xsd" />
  <import namespace="http://xbrl.sec.gov/cef/2025" schemaLocation="https://xbrl.sec.gov/cef/2025/cef-2025.xsd" />
  <import namespace="http://xbrl.sec.gov/cef-pre/2025" schemaLocation="https://xbrl.sec.gov/cef/2025/cef-2025_pre.xsd" />
  <element name="ArpsMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="cik0001190935_ArpsMember" substitutionGroup="xbrli:item" />
  <element name="CommonSharesMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="cik0001190935_CommonSharesMember" substitutionGroup="xbrli:item" />
</schema>
